fix(#497): @[name] is a verbatim wire token, remove the trim

Owner ruling 2026-08-01. Mention autocomplete trimmed the contact name
when building the @[...] token while the device stores and matches it
byte-for-byte, so any name with leading or trailing whitespace was
unmentionable and never beeped. Confirmed on the wire: the contact
record keeps the 0x20, the outgoing mention drops it.

@[...] is a wire token, not display text. Entry, firmware memcpy,
advert encode, advert parse and the contact record are all verbatim by
design; this trim was the only transformation applied to a node name
anywhere, and it changed the identity of the addressee.

- MentionCandidate now separates the two concerns: `name` is raw and
  goes on the wire, `label` is display-only and may be tidied. The
  const constructor is preserved, so existing const call sites still
  compile.
- The candidate builder keeps sender and contact names raw. Emptiness is
  probed on a trimmed copy; the stored value is untouched.
- _mentionsSelf drops its own trim as a direct consequence: a raw token
  requires a raw comparison, or this node stops recognising mentions of
  its own name.
- Contract clause written at both the insertion site and _mentionsSelf,
  stating the token is byte-for-byte and that a future .trim() tidy-up
  is forbidden. The contract was silent on raw vs normalised, which is
  why both sides were reasonable and incompatible.

Deliberately out of scope per the ruling: no entry-side trim in
settings_screen. It fixes no deployed name and would silently alter
deliberate spacing.

Test updated to assert the new truth: '  Ben  ' does NOT match @[Ben],
and DOES match @[  Ben  ]. Full suite 732 pass, analyze clean.

Agent: CalmBay (session d14220d9)

lib/connector/meshcore_connector.dart

@@ -6178,17 +6178,25 @@ class MeshCoreConnector extends ChangeNotifier {
   /// change that ships only in an aligned client + firmware build pair, never
   /// unilaterally.
   ///
-  /// The three properties firmware must match, none obvious from the rule name:
+  /// ⚠ THE NAME IS COMPARED VERBATIM. Owner ruling 2026-08-01 (#497): the
-  /// the name is trimmed and an empty name matches nothing (it does not fall
+  /// `@[name]` token carries the advert name BYTE-FOR-BYTE, unnormalised. No
-  /// through to matching everything); the match is a plain substring `contains`,
+  /// trimming, no Unicode normalisation. Leading and trailing whitespace are
-  /// neither anchored nor word-boundary aware; folding is ASCII-only per
+  /// part of a name's identity, and every other hop is already verbatim, so a
-  /// [_foldAscii].
+  /// `.trim()` here makes this node stop recognising mentions of itself. That
+  /// is what stopped mentions beeping. Do not reintroduce it.
+  ///
+  /// The properties firmware must match, none obvious from the rule name: an
+  /// empty name matches nothing (it does not fall through to matching
+  /// everything); the match is a plain substring `contains`, neither anchored
+  /// nor word-boundary aware; folding is ASCII-only per [_foldAscii] and is the
+  /// ONLY normalisation applied to either side.
   ///
   /// Bare `@Name` is deliberately NOT matched: it false-positives on ordinary
   /// text and cannot be delimited for names containing spaces.
   static bool mentionsName(String text, String? selfName) {
-    final name = selfName?.trim();
+    final name = selfName;
-    if (name == null || name.isEmpty) return false;
+    // Emptiness is probed on a trimmed copy; the COMPARISON uses the raw name.
+    if (name == null || name.trim().isEmpty) return false;
     return _foldAscii(text).contains('@[${_foldAscii(name)}]');
   }
 

lib/screens/channel_chat_screen.dart

@@ -1297,11 +1297,15 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
     final seen = <String>{};
 
     // Recent senders in this channel, keyed to their most recent timestamp.
+    // Names are carried VERBATIM: the `@[name]` token must byte-match the
+    // advert name the device stores, whitespace included (#497). Emptiness is
+    // tested on a trimmed copy, but the raw name is what gets kept.
     final recentTime = <String, DateTime>{};
     for (final message in connector.getChannelMessages(_currentChannel)) {
       if (message.isOutgoing) continue;
-      final name = message.senderName.trim();
+      final name = message.senderName;
-      if (name.isEmpty || name == 'Unknown') continue;
+      final probe = name.trim();
+      if (probe.isEmpty || probe == 'Unknown') continue;
       final existing = recentTime[name];
       if (existing == null || message.timestamp.isAfter(existing)) {
         recentTime[name] = message.timestamp;
@@ -1314,10 +1318,11 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
       seen.add(name.toLowerCase());
     });
 
-    // Known contacts not already present as a recent sender.
+    // Known contacts not already present as a recent sender. Same rule: the
+    // contact's name is kept raw so the inserted token matches the device.
     for (final contact in connector.allContacts) {
-      final name = contact.name.trim();
+      final name = contact.name;
-      if (name.isEmpty) continue;
+      if (name.trim().isEmpty) continue;
       if (!seen.add(name.toLowerCase())) continue;
       candidates.add(MentionCandidate(name: name, recent: false));
     }

lib/widgets/mention_autocomplete.dart

@@ -5,6 +5,17 @@ import 'byte_count_input.dart';
 
 /// A candidate name for `@`-mention autocomplete.
 class MentionCandidate {
+  /// The advert name EXACTLY as the device holds it, including any leading or
+  /// trailing whitespace.
+  ///
+  /// ⚠ CROSS-REPO CONTRACT (client #497, firmware #510). The `@[name]` token
+  /// carries the advert name BYTE-FOR-BYTE, unnormalised: no trimming, no
+  /// Unicode normalisation, no case folding when composing it. Whitespace is
+  /// part of a name's identity, and every other hop (entry, firmware memcpy,
+  /// advert encode, advert parse, contact record) is already verbatim. A
+  /// `.trim()` here changes the identity of the addressee and makes the
+  /// mention unmatchable on the device, which is exactly the bug that stopped
+  /// mentions beeping. Do not "tidy" this.
   final String name;
 
   /// True when this name is a recent sender in the current channel.
@@ -13,11 +24,17 @@ class MentionCandidate {
   /// Most-recent time this name was seen (recent candidates only).
   final DateTime? lastSeen;
 
+  final String? _label;
+
+  /// Display-only form. Safe to trim, because it never reaches the wire.
+  String get label => _label ?? name.trim();
+
   const MentionCandidate({
     required this.name,
+    String? label,
     required this.recent,
     this.lastSeen,
-  });
+  }) : _label = label;
 }
 
 /// One row in the autocomplete dropdown.
@@ -248,8 +265,11 @@ class _MentionAutocompleteFieldState extends State<MentionAutocompleteField> {
     }
     _matches = combined
         .map(
+          // label is display, insert is the wire token. They are deliberately
+          // different fields: the token must carry the raw name verbatim while
+          // the list may show a tidied one. (#497)
           (c) => _Entry(
-            label: c.name,
+            label: c.label,
             icon: c.recent ? Icons.history : Icons.person_outline,
             insert: '@[${c.name}] ',
           ),

test/connector/mention_contract_test.dart

@@ -26,8 +26,17 @@ void main() {
       expect(MeshCoreConnector.mentionsName('x@[Ben]y', 'Ben'), isTrue);
     });
 
-    test('name is trimmed before matching', () {
+    test('the name is compared VERBATIM, whitespace included (#497)', () {
-      expect(MeshCoreConnector.mentionsName('yo @[Ben]', '  Ben  '), isTrue);
+      // Owner ruling 2026-08-01: @[name] is a wire token carrying the advert
+      // name byte-for-byte. A name with surrounding spaces is a DIFFERENT
+      // name, and trimming it here is what stopped mentions beeping.
+      expect(MeshCoreConnector.mentionsName('yo @[Ben]', '  Ben  '), isFalse);
+      expect(
+        MeshCoreConnector.mentionsName('yo @[  Ben  ]', '  Ben  '),
+        isTrue,
+      );
+      expect(MeshCoreConnector.mentionsName('yo @[Ben ]', 'Ben '), isTrue);
+      expect(MeshCoreConnector.mentionsName('yo @[Ben]', 'Ben '), isFalse);
     });
 
     test('empty or whitespace-only self-name matches nothing', () {