fix(#150): trace flood/empty paths as a direct ping (was sending empty -> firmware error 1)

App Debug Log showed every failing trace sending an empty path ->
"Firmware responded with error code: 1". Cause: repeaters with a flood
route (path stored as all-zeros) were treated as routed; buildPath
collapsed the all-zero path to empty; the firmware rejects an empty trace.

- buildPath: an empty OR all-zero path now traces the target's own width
  prefix (never returns an empty payload).
- _doPathTrace: guard - never send an empty path; surface "not available".
- Repeater menu: constant "Path Trace" label (no more Ping/Path-Trace
  flip-flop); a flood path (all-zero) counts as no route -> direct ping.

Bumps build to +50 for the b50 test binary.

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

lib/screens/contacts_screen.dart

@@ -1266,31 +1266,32 @@ class _ContactsScreenState extends State<ContactsScreen>
             if (isRepeater) ...[
               ListTile(
                 leading: const Icon(Icons.radar, color: Colors.green),
-                title: Text(
-                  contact.pathBytesForDisplay.isNotEmpty
-                      ? context.l10n.contacts_pathTrace
-                      : context.l10n.contacts_ping,
-                ),
+                title: Text(context.l10n.contacts_pathTrace),
                 onTap: () {
                   final hw = context
                       .read<MeshCoreConnector>()
                       .pathHashByteWidth;
+                  // A flood route is stored as all-zero bytes = "no real route",
+                  // so trace the target directly instead of routing through (and
+                  // sending) an all-zero/empty path. (#150)
+                  final route = contact.pathBytesForDisplay;
+                  final hasRoute = route.isNotEmpty && route.any((b) => b != 0);
                   Navigator.push(
                     context,
                     MaterialPageRoute(
                       builder: (context) => PathTraceMapScreen(
-                        title: contact.pathBytesForDisplay.isNotEmpty
+                        title: hasRoute
                             ? context.l10n.contacts_repeaterPathTrace
                             : context.l10n.contacts_repeaterPing,
-                        path: contact.pathBytesForDisplay.isNotEmpty
-                            ? contact.pathBytesForDisplay
+                        path: hasRoute
+                            ? route
                             : Uint8List.fromList(
                                 contact.publicKey.sublist(
                                   0,
                                   PathHelper.traceHopBytes(hw),
                                 ),
                               ),
-                        flipPathAround: contact.pathBytesForDisplay.isNotEmpty,
+                        flipPathAround: hasRoute,
                         targetContact: contact,
                         pathHashByteWidth: hw,
                       ),

lib/screens/path_trace_map.dart

@@ -199,17 +199,15 @@ class _PathTraceMapScreenState extends State<PathTraceMapScreen> {
     final hopBytes = PathHelper.traceHopBytes(widget.pathHashByteWidth);
     final pk = widget.targetContact?.publicKey;
 
-    if (pathBytes.isEmpty) {
-      // Direct target: send its own width prefix.
+    // Empty path, or an all-zero "flood" marker, means no real route — trace
+    // the target's own width prefix directly. Never return an empty payload:
+    // the firmware rejects an empty trace with error 1. (#150)
+    if (pathBytes.isEmpty || pathBytes.every((b) => b == 0)) {
       if (pk != null && pk.length >= hopBytes) {
         return Uint8List.fromList(pk.sublist(0, hopBytes));
       }
       return Uint8List.fromList([pk != null && pk.isNotEmpty ? pk[0] : 0]);
     }
-    // An all-zero path is the "no known path" marker → no trace payload.
-    if (pathBytes.every((b) => b == 0)) {
-      return Uint8List(0);
-    }
 
     final throughTarget =
         widget.targetContact?.type == advTypeRepeater ||
@@ -246,6 +244,23 @@ class _PathTraceMapScreenState extends State<PathTraceMapScreen> {
 
     final path = widget.flipPathAround ? buildPath(pathTmp) : pathTmp;
 
+    if (path.isEmpty) {
+      // No route to trace — don't send an empty payload (firmware error 1);
+      // surface "not available" instead. (#150)
+      appLogger.info(
+        'Path trace skipped: no route to trace',
+        tag: 'PathTraceMapScreen',
+        noNotify: !mounted,
+      );
+      if (mounted) {
+        setState(() {
+          _isLoading = false;
+          _failed2Loaded = true;
+        });
+      }
+      return;
+    }
+
     appLogger.info(
       'Initiating path trace with path: ${_formatPathPrefixes(path)}',
       tag: 'PathTraceMapScreen',

pubspec.yaml

@@ -16,7 +16,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 # https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
 # In Windows, build-name is used as the major, minor, and patch parts
 # of the product and file versions while build-number is used as the build suffix.
-version: 1.1.2-rc.1+49
+version: 1.1.2-rc.1+50
 
 environment:
   sdk: ^3.9.2