fix(#155): manual path entry honors the configured path-hash width

The "Set Path" dialog parsed, built, and displayed hop prefixes as a fixed
1 byte (substring(0,2)), so on a 2-/3-byte path-hash mesh manual entry produced
wrong-width routing paths and the helper text claimed "1 byte". Make it width-
aware from connector.pathHashByteWidth.

- parsePathPrefixes(text, width, invalid): static + testable; each entry must be
  EXACTLY width*2 hex chars (wrong-length / malformed go to invalid, never
  silently truncated); width clamped >= 1.
- _updateTextFromContacts / display / maxLength group by the configured width;
  the display substring is guarded against short keys.
- show() takes pathHashByteWidth; the chat + path-management callers pass
  connector.pathHashByteWidth.
- l10n: reworded the path-entry helper / example / instructions to be width-
  agnostic (dropped the "2 hex / 1 byte / first byte" claims). The 17 non-English
  locales keep their prior strings, flagged for re-translation (English fixed).

analyze clean; 6 parsePathPrefixes tests (incl. exact-length + clamp). Gemini v1
BLOCKER (unguarded substring) + MAJOR (silent truncation) fixed; v2 MAJORs were
the pre-existing refresh button (out of scope), v2 MINOR (1-byte example) fixed.

Closes #155

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/l10n/app_en.arb

@@ -1151,10 +1151,10 @@
   },
   "path_enterCustomPath": "Enter Custom Path",
   "path_currentPathLabel": "Current path",
-  "path_hexPrefixInstructions": "Enter 2-character hex prefixes for each hop, separated by commas.",
-  "path_hexPrefixExample": "Example: A1,F2,3C (each node uses first byte of its public key)",
+  "path_hexPrefixInstructions": "Enter each hop's hex prefix, separated by commas.",
+  "path_hexPrefixExample": "Tap nodes below, or enter each hop's hex prefix, comma-separated.",
   "path_labelHexPrefixes": "Path (hex prefixes)",
-  "path_helperMaxHops": "Max 64 hops. Each prefix is 2 hex characters (1 byte)",
+  "path_helperMaxHops": "Max 64 hops.",
   "path_selectFromContacts": "Or select from contacts:",
   "path_noRepeatersFound": "No repeaters or room servers found.",
   "path_customPathsRequire": "Custom paths require intermediate hops that can relay messages.",

lib/l10n/app_localizations.dart

@@ -3834,13 +3834,13 @@ abstract class AppLocalizations {
   /// No description provided for @path_hexPrefixInstructions.
   ///
   /// In en, this message translates to:
-  /// **'Enter 2-character hex prefixes for each hop, separated by commas.'**
+  /// **'Enter each hop\'s hex prefix, separated by commas.'**
   String get path_hexPrefixInstructions;
 
   /// No description provided for @path_hexPrefixExample.
   ///
   /// In en, this message translates to:
-  /// **'Example: A1,F2,3C (each node uses first byte of its public key)'**
+  /// **'Tap nodes below, or enter each hop\'s hex prefix, comma-separated.'**
   String get path_hexPrefixExample;
 
   /// No description provided for @path_labelHexPrefixes.
@@ -3852,7 +3852,7 @@ abstract class AppLocalizations {
   /// No description provided for @path_helperMaxHops.
   ///
   /// In en, this message translates to:
-  /// **'Max 64 hops. Each prefix is 2 hex characters (1 byte)'**
+  /// **'Max 64 hops.'**
   String get path_helperMaxHops;
 
   /// No description provided for @path_selectFromContacts.

lib/l10n/app_localizations_en.dart

@@ -2104,18 +2104,17 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get path_hexPrefixInstructions =>
-      'Enter 2-character hex prefixes for each hop, separated by commas.';
+      'Enter each hop\'s hex prefix, separated by commas.';
 
   @override
   String get path_hexPrefixExample =>
-      'Example: A1,F2,3C (each node uses first byte of its public key)';
+      'Tap nodes below, or enter each hop\'s hex prefix, comma-separated.';
 
   @override
   String get path_labelHexPrefixes => 'Path (hex prefixes)';
 
   @override
-  String get path_helperMaxHops =>
-      'Max 64 hops. Each prefix is 2 hex characters (1 byte)';
+  String get path_helperMaxHops => 'Max 64 hops.';
 
   @override
   String get path_selectFromContacts => 'Or select from contacts:';

lib/screens/chat_screen.dart

@@ -1513,6 +1513,7 @@ class _ChatScreenState extends State<ChatScreen> {
     final result = await PathSelectionDialog.show(
       context,
       availableContacts: availableContacts,
+      pathHashByteWidth: connector.pathHashByteWidth,
       initialPath: pathForInput.isEmpty ? null : pathForInput,
       title: context.l10n.chat_setCustomPath,
       currentPathLabel: currentPathLabel,

lib/widgets/path_management_dialog.dart

@@ -152,6 +152,7 @@ class _PathManagementDialogState extends State<_PathManagementDialog> {
     final result = await PathSelectionDialog.show(
       context,
       availableContacts: availableContacts,
+      pathHashByteWidth: connector.pathHashByteWidth,
       initialPath: pathForInput.isEmpty ? null : pathForInput,
       currentPathLabel: currentContact.pathLabel(l10n),
       onRefresh: connector.isConnected ? connector.getContacts : null,

lib/widgets/path_selection_dialog.dart

@@ -12,11 +12,13 @@ class PathSelectionDialog extends StatefulWidget {
   final String? initialPath;
   final String? currentPathLabel;
   final VoidCallback? onRefresh;
+  final int pathHashByteWidth;
 
   const PathSelectionDialog({
     super.key,
     required this.availableContacts,
     required this.title,
+    required this.pathHashByteWidth,
     this.initialPath,
     this.currentPathLabel,
     this.onRefresh,
@@ -28,6 +30,7 @@ class PathSelectionDialog extends StatefulWidget {
   static Future<Uint8List?> show(
     BuildContext context, {
     required List<Contact> availableContacts,
+    required int pathHashByteWidth,
     String? title,
     String? initialPath,
     String? currentPathLabel,
@@ -37,6 +40,7 @@ class PathSelectionDialog extends StatefulWidget {
       context: context,
       builder: (context) => PathSelectionDialog(
         availableContacts: availableContacts,
+        pathHashByteWidth: pathHashByteWidth,
         title: title ?? context.l10n.path_enterCustomPath,
         initialPath: initialPath,
         currentPathLabel: currentPathLabel,
@@ -44,6 +48,33 @@ class PathSelectionDialog extends StatefulWidget {
       ),
     );
   }
+
+  /// Parses comma-separated hex hop prefixes, each exactly [hashWidth] bytes
+  /// wide (clamped >= 1). Wrong-length or malformed entries go to [invalid] and
+  /// are skipped — never silently truncated. (#155)
+  static List<int> parsePathPrefixes(
+    String text,
+    int hashWidth,
+    List<String> invalid,
+  ) {
+    final hexLen = (hashWidth < 1 ? 1 : hashWidth) * 2;
+    final bytes = <int>[];
+    for (final id
+        in text.split(',').map((s) => s.trim()).where((s) => s.isNotEmpty)) {
+      if (id.length != hexLen) {
+        invalid.add(id);
+        continue;
+      }
+      try {
+        for (var i = 0; i < hexLen; i += 2) {
+          bytes.add(int.parse(id.substring(i, i + 2), radix: 16));
+        }
+      } catch (_) {
+        invalid.add(id);
+      }
+    }
+    return bytes;
+  }
 }
 
 class _PathSelectionDialogState extends State<PathSelectionDialog> {
@@ -51,6 +82,12 @@ class _PathSelectionDialogState extends State<PathSelectionDialog> {
   final List<Contact> _selectedContacts = [];
   List<Contact> _validContacts = [];
 
+  // Hop prefix width in bytes (clamped >= 1) and in hex chars, from the device's
+  // configured path-hash width. (#155)
+  int get _hopWidth =>
+      widget.pathHashByteWidth < 1 ? 1 : widget.pathHashByteWidth;
+  int get _hexLen => _hopWidth * 2;
+
   @override
   void initState() {
     super.initState();
@@ -73,10 +110,11 @@ class _PathSelectionDialogState extends State<PathSelectionDialog> {
   }
 
   void _updateTextFromContacts() {
+    final hexLen = _hexLen;
     final pathParts = _selectedContacts
         .map((contact) {
-          if (contact.publicKeyHex.length >= 2) {
-            return contact.publicKeyHex.substring(0, 2);
+          if (contact.publicKeyHex.length >= hexLen) {
+            return contact.publicKeyHex.substring(0, hexLen);
           }
           return '';
         })
@@ -112,29 +150,13 @@ class _PathSelectionDialogState extends State<PathSelectionDialog> {
       return;
     }
 
-    // Parse comma-separated hex prefixes
-    final pathIds = path
-        .split(',')
-        .map((s) => s.trim())
-        .where((s) => s.isNotEmpty)
-        .toList();
-    final pathBytesList = <int>[];
+    // Parse comma-separated hex prefixes, each exactly one path-hash hop wide.
     final invalidPrefixes = <String>[];
-
-    for (final id in pathIds) {
-      if (id.length < 2) {
-        invalidPrefixes.add(id);
-        continue;
-      }
-
-      final prefix = id.substring(0, 2);
-      try {
-        final byte = int.parse(prefix, radix: 16);
-        pathBytesList.add(byte);
-      } catch (e) {
-        invalidPrefixes.add(id);
-      }
-    }
+    final pathBytesList = PathSelectionDialog.parsePathPrefixes(
+      path,
+      widget.pathHashByteWidth,
+      invalidPrefixes,
+    );
 
     if (!mounted) return;
 
@@ -150,7 +172,7 @@ class _PathSelectionDialogState extends State<PathSelectionDialog> {
     }
 
     // Check max path length (64 hops)
-    if (pathBytesList.length > 64) {
+    if (pathBytesList.length > 64 * _hopWidth) {
       showDismissibleSnackBar(
         context,
         content: Text(l10n.path_tooLong),
@@ -227,7 +249,7 @@ class _PathSelectionDialogState extends State<PathSelectionDialog> {
                   helperText: l10n.path_helperMaxHops,
                 ),
                 textCapitalization: TextCapitalization.characters,
-                maxLength: 191, // 64 hops * 2 chars + 63 commas
+                maxLength: 64 * _hexLen + 63, // 64 hops * (width*2) + 63 commas
               ),
               const SizedBox(height: 16),
               const Divider(),
@@ -312,7 +334,7 @@ class _PathSelectionDialogState extends State<PathSelectionDialog> {
                           style: const TextStyle(fontSize: 14),
                         ),
                         subtitle: Text(
-                          '${contact.typeLabel(l10n)} • ${contact.publicKeyHex.substring(0, 2)}',
+                          '${contact.typeLabel(l10n)} • ${contact.publicKeyHex.length >= _hexLen ? contact.publicKeyHex.substring(0, _hexLen) : contact.publicKeyHex}',
                           style: const TextStyle(fontSize: 10),
                         ),
                         trailing: isSelected

test/widgets/path_selection_dialog_test.dart

@@ -0,0 +1,57 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_open/widgets/path_selection_dialog.dart';
+
+void main() {
+  group('PathSelectionDialog.parsePathPrefixes (#155)', () {
+    test('width 1 — single-byte hops', () {
+      final invalid = <String>[];
+      expect(PathSelectionDialog.parsePathPrefixes('A1,F2,3C', 1, invalid), [
+        0xA1,
+        0xF2,
+        0x3C,
+      ]);
+      expect(invalid, isEmpty);
+    });
+
+    test('width 2 — two-byte hops, each entry 4 hex chars', () {
+      final invalid = <String>[];
+      expect(PathSelectionDialog.parsePathPrefixes('84AB,C1D2', 2, invalid), [
+        0x84,
+        0xAB,
+        0xC1,
+        0xD2,
+      ]);
+      expect(invalid, isEmpty);
+    });
+
+    test('wrong-length entries are rejected, never silently truncated', () {
+      final invalid = <String>[];
+      // too short (1 byte) and too long (3 bytes) on a 2-byte mesh
+      final bytes = PathSelectionDialog.parsePathPrefixes(
+        '84,AABBCC',
+        2,
+        invalid,
+      );
+      expect(bytes, isEmpty);
+      expect(invalid, ['84', 'AABBCC']);
+    });
+
+    test('non-hex entry is rejected', () {
+      final invalid = <String>[];
+      PathSelectionDialog.parsePathPrefixes('ZZ', 1, invalid);
+      expect(invalid, ['ZZ']);
+    });
+
+    test('width < 1 is clamped to 1', () {
+      final invalid = <String>[];
+      expect(PathSelectionDialog.parsePathPrefixes('A1', 0, invalid), [0xA1]);
+      expect(invalid, isEmpty);
+    });
+
+    test('empty input → empty path', () {
+      final invalid = <String>[];
+      expect(PathSelectionDialog.parsePathPrefixes('', 2, invalid), isEmpty);
+      expect(invalid, isEmpty);
+    });
+  });
+}