fix(#528): apply the three accepted Gemini review findings

1. An unprefixed reply no longer resolves an arbitrary pending command.
   #532 constrained prefixed replies only; the unprefixed fallback still
   used firstWhere, which with two or more in flight is map-iteration
   order, so a caller could receive another command's output. The
   fallback cannot just be deleted: firmware only echoes the prefix when
   the command exceeds four characters including it
   (simple_repeater/MyMesh.cpp, strlen(command) > 4 && command[2] == '|'),
   so a very short command legitimately answers without one. It now
   resolves only when exactly one command is pending, and surfaces the
   ambiguity otherwise.

2. A late reply no longer overwrites unsaved edits. The settings screen
   applied a late `get` payload unconditionally, so a reply arriving after
   its timeout could revert a field the user had typed into while waiting.
   It now applies only when nothing is dirty, and says which happened.

3. _expiredCommands is pruned on timeout as well as on receive. It was
   pruned only in handleResponse, so a run of commands that all time out
   with no traffic coming back accumulated records until disposal.

The reviewer described 3 as unbounded growth. It is bounded at 256 by the
prefix token space, and stale records could never be mis-attributed
because handleResponse prunes before matching, so the severity was
overstated. Fixed anyway; it is nearly free.

A fourth finding, that the new l10n strings are untranslated in the other
17 locales, is rejected. That is this project's established pipeline:
strings are authored in app_en.arb, gen-l10n emits English fallbacks, and
untranslated.json tracks the gap, which it now does for these keys. Every
string in the app arrived this way, so it is not a defect this branch
introduces.

The ambiguity test was verified to fail against the pre-fix code.

lib/l10n/app_en.arb

@@ -1586,6 +1586,7 @@
     }
   },
   "repeater_cliUnmatchedResponse": "Unrequested response from repeater",
+  "repeater_lateResponseDiscarded": "A late response arrived but was not applied, because you have unsaved changes.",
   "repeater_lateResponseReceived": "A late response arrived after the command timed out. See the CLI screen.",
   "repeater_cliQuickGetName": "Get Name",
   "repeater_cliQuickGetRadio": "Get Radio",

lib/l10n/app_localizations.dart

@@ -5144,6 +5144,12 @@ abstract class AppLocalizations {
   /// **'Unrequested response from repeater'**
   String get repeater_cliUnmatchedResponse;
 
+  /// No description provided for @repeater_lateResponseDiscarded.
+  ///
+  /// In en, this message translates to:
+  /// **'A late response arrived but was not applied, because you have unsaved changes.'**
+  String get repeater_lateResponseDiscarded;
+
   /// No description provided for @repeater_lateResponseReceived.
   ///
   /// In en, this message translates to:

lib/l10n/app_localizations_bg.dart

@@ -2919,6 +2919,10 @@ class AppLocalizationsBg extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_de.dart

@@ -2922,6 +2922,10 @@ class AppLocalizationsDe extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_en.dart

@@ -2863,6 +2863,10 @@ class AppLocalizationsEn extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_es.dart

@@ -2913,6 +2913,10 @@ class AppLocalizationsEs extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_fr.dart

@@ -2935,6 +2935,10 @@ class AppLocalizationsFr extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_hu.dart

@@ -2926,6 +2926,10 @@ class AppLocalizationsHu extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_it.dart

@@ -2919,6 +2919,10 @@ class AppLocalizationsIt extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_ja.dart

@@ -2799,6 +2799,10 @@ class AppLocalizationsJa extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_ko.dart

@@ -2797,6 +2797,10 @@ class AppLocalizationsKo extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_nl.dart

@@ -2899,6 +2899,10 @@ class AppLocalizationsNl extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_pl.dart

@@ -2927,6 +2927,10 @@ class AppLocalizationsPl extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_pt.dart

@@ -2911,6 +2911,10 @@ class AppLocalizationsPt extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_ru.dart

@@ -2917,6 +2917,10 @@ class AppLocalizationsRu extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_sk.dart

@@ -2898,6 +2898,10 @@ class AppLocalizationsSk extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_sl.dart

@@ -2897,6 +2897,10 @@ class AppLocalizationsSl extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_sv.dart

@@ -2883,6 +2883,10 @@ class AppLocalizationsSv extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_uk.dart

@@ -2915,6 +2915,10 @@ class AppLocalizationsUk extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/l10n/app_localizations_zh.dart

@@ -2751,6 +2751,10 @@ class AppLocalizationsZh extends AppLocalizations {
   String get repeater_cliUnmatchedResponse =>
       'Unrequested response from repeater';
 
+  @override
+  String get repeater_lateResponseDiscarded =>
+      'A late response arrived but was not applied, because you have unsaved changes.';
+
   @override
   String get repeater_lateResponseReceived =>
       'A late response arrived after the command timed out. See the CLI screen.';

lib/screens/repeater_settings_screen.dart

@@ -194,12 +194,20 @@ class _RepeaterSettingsScreenState extends State<RepeaterSettingsScreen> {
   /// (#528).
   void _handleUnmatchedResponse(UnmatchedRepeaterResponse unmatched) {
     if (!mounted) return;
-    if (unmatched.command != null) {
-      _handleGetResponse(unmatched.command!, unmatched.response);
-    }
+    // A late reply is stale by definition. Applying it over edits the user
+    // made while waiting would silently discard their input, so it only lands
+    // when nothing is unsaved (Gemini review).
+    final applied =
+        !_hasChanges &&
+        unmatched.command != null &&
+        _handleGetResponse(unmatched.command!, unmatched.response);
     showDismissibleSnackBar(
       context,
-      content: Text(context.l10n.repeater_lateResponseReceived),
+      content: Text(
+        applied
+            ? context.l10n.repeater_lateResponseReceived
+            : context.l10n.repeater_lateResponseDiscarded,
+      ),
     );
   }
 

lib/services/repeater_command_service.dart

@@ -166,6 +166,11 @@ class RepeaterCommandService {
         () {
           final completer = _pendingCommands[commandId];
           if (completer != null && !completer.isCompleted) {
+            // Prune here as well as on receive. A run of commands that all
+            // time out with no traffic coming back would otherwise accumulate
+            // records until disposal, since handleResponse is the only other
+            // place that prunes and it never runs (Gemini review).
+            _pruneExpiredCommands();
             // Remember what this prefix asked so a reply arriving after the
             // window can still reach the user with its question attached.
             _expiredCommands[prefix] = _ExpiredCommand(
@@ -211,13 +216,7 @@ class RepeaterCommandService {
     // to matching by repeater.
     final matchedId = prefix != null ? _pendingByPrefix[prefix] : null;
     final commandId =
-        matchedId ??
-        (prefix != null
-            ? ''
-            : _pendingCommands.keys.firstWhere(
-                (id) => id.startsWith(repeaterKey),
-                orElse: () => '',
-              ));
+        matchedId ?? (prefix != null ? '' : _solePendingFor(repeaterKey));
 
     if (commandId.isNotEmpty) {
       final completer = _pendingCommands[commandId];
@@ -267,6 +266,28 @@ class RepeaterCommandService {
     );
   }
 
+  /// The one command awaiting a reply from [repeaterKey], or `''` when that is
+  /// ambiguous.
+  ///
+  /// An unprefixed reply carries no correlation token, so position is all that
+  /// is left to match on. Firmware only echoes the prefix when the command is
+  /// longer than four characters including it (`simple_repeater/MyMesh.cpp`
+  /// `strlen(command) > 4 && command[2] == '|'`), so a very short command can
+  /// legitimately answer without one and the fallback has to stay.
+  ///
+  /// It is only sound with exactly one candidate though. With two or more,
+  /// "first" is map-iteration order, and choosing one would hand a caller
+  /// another command's output. Ambiguity is surfaced instead of guessed.
+  String _solePendingFor(String repeaterKey) {
+    String? only;
+    for (final id in _pendingCommands.keys) {
+      if (!id.startsWith(repeaterKey)) continue;
+      if (only != null) return '';
+      only = id;
+    }
+    return only ?? '';
+  }
+
   Completer<String> _registerPending(String commandId, String prefix) {
     final completer = Completer<String>();
     _pendingCommands[commandId] = completer;

test/services/repeater_command_service_test.dart

@@ -221,4 +221,57 @@ void main() {
       expect(surfaced, isEmpty);
     });
   });
+
+  group('unprefixed reply ambiguity (Gemini review)', () {
+    // #532 constrained PREFIXED replies. An unprefixed one still fell back to
+    // "first pending command for this repeater", which with two or more in
+    // flight is map-iteration order, so a caller could receive another
+    // command's output.
+    //
+    // The fallback cannot simply be deleted: firmware only echoes the prefix
+    // when the command exceeds four characters including it
+    // (simple_repeater/MyMesh.cpp, `strlen(command) > 4 && command[2] == '|'`),
+    // so a very short command legitimately replies without one.
+
+    test(
+      'with exactly one pending, an unprefixed reply still resolves it',
+      () async {
+        final only = service.registerPendingForTest(
+          repeater.publicKeyHex,
+          'E1|',
+        );
+
+        service.handleResponse(repeater, 'bare payload');
+
+        expect(await only, 'bare payload');
+        expect(surfaced, isEmpty);
+      },
+    );
+
+    test('with two pending, an unprefixed reply resolves NEITHER', () async {
+      final first = service.registerPendingForTest(
+        repeater.publicKeyHex,
+        'E1|',
+      );
+      final second = service.registerPendingForTest(
+        repeater.publicKeyHex,
+        'E2|',
+      );
+      var firstDone = false, secondDone = false;
+      unawaited(first.then((_) => firstDone = true));
+      unawaited(second.then((_) => secondDone = true));
+
+      service.handleResponse(repeater, 'ambiguous payload');
+      await Future<void>.delayed(Duration.zero);
+
+      expect(firstDone, isFalse);
+      expect(secondDone, isFalse);
+      expect(
+        surfaced.single.response,
+        'ambiguous payload',
+        reason: 'ambiguity must be surfaced, never guessed at',
+      );
+      expect(surfaced.single.command, isNull);
+    });
+  });
 }