fix(android): polish app chrome and join guard

apps/chanora_flutter/android/app/src/main/kotlin/app/chanora/chanora_flutter/MainActivity.kt

@@ -1,7 +1,10 @@
 package app.chanora.chanora_flutter
 
 import android.content.Context
+import android.graphics.Color
+import android.os.Build
 import android.os.Bundle
+import android.view.View
 import app.chanora.chanora_flutter.AndroidPermissionRequester
 import app.chanora.chanora_flutter.BackIntentBridge
 import app.chanora.chanora_flutter.MethodChannels
@@ -76,6 +79,11 @@ class MainActivity : FlutterActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+        window.navigationBarColor = Color.rgb(255, 251, 254)
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            window.decorView.systemUiVisibility =
+                window.decorView.systemUiVisibility or View.SYSTEM_UI_FLAG_LIGHT_NAVIGATION_BAR
+        }
         // SDD-105: pass the Application context to the Rust side so the
         // audio engine can open device handles. Must run on the main thread
         // before any `chanora_audio` call from Dart. The native library is

apps/chanora_flutter/lib/main.dart

@@ -31,6 +31,8 @@ import 'widgets/voice_settings.dart';
 
 bool get _isMacOS => !kIsWeb && Platform.isMacOS;
 
+const Color _appSurfaceColor = Color(0xFFFFFBFE);
+
 /// Top padding for macOS to clear traffic-light buttons.
 const double _macOSTrafficLightPad = 56.0;
 
@@ -205,19 +207,29 @@ class ChanoraApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
-      onGenerateTitle: (ctx) => AppL10n.of(ctx).appTitle,
-      // No "DEBUG" banner in the top-right corner. This is purely
-      // cosmetic for the developer-build experience; release builds
-      // never render it regardless of this flag.
-      debugShowCheckedModeBanner: false,
-      theme: ThemeData(
-        useMaterial3: true,
-        colorSchemeSeed: const Color(0xFF3F51B5),
+    return AnnotatedRegion<SystemUiOverlayStyle>(
+      value: const SystemUiOverlayStyle(
+        statusBarColor: Colors.transparent,
+        statusBarIconBrightness: Brightness.dark,
+        systemNavigationBarColor: _appSurfaceColor,
+        systemNavigationBarDividerColor: _appSurfaceColor,
+        systemNavigationBarIconBrightness: Brightness.dark,
+      ),
+      child: MaterialApp(
+        onGenerateTitle: (ctx) => AppL10n.of(ctx).appTitle,
+        // No "DEBUG" banner in the top-right corner. This is purely
+        // cosmetic for the developer-build experience; release builds
+        // never render it regardless of this flag.
+        debugShowCheckedModeBanner: false,
+        theme: ThemeData(
+          useMaterial3: true,
+          colorSchemeSeed: const Color(0xFF3F51B5),
+          scaffoldBackgroundColor: _appSurfaceColor,
+        ),
+        localizationsDelegates: AppL10n.localizationsDelegates,
+        supportedLocales: AppL10n.supportedLocales,
+        home: const _BetaHome(),
       ),
-      localizationsDelegates: AppL10n.localizationsDelegates,
-      supportedLocales: AppL10n.supportedLocales,
-      home: const _BetaHome(),
     );
   }
 }
@@ -703,6 +715,7 @@ class _BetaHomeState extends State<_BetaHome> {
       password = await _askChannelPassword(l10n);
       if (password == null) return; // cancelled
     }
+    setState(() => _pendingVoiceChannelId = ch.id);
     try {
       // SDD-106 §1, §6 + SRS-209: Android runtime permission gate.
       // Request RECORD_AUDIO at or before voice_join. On denial or
@@ -756,6 +769,7 @@ class _BetaHomeState extends State<_BetaHome> {
       // is selected by TS3 error code per the canonical
       // catalogue at https://github.com/ReSpeak/tsdeclarations.
       final message = _channelJoinErrorMessage(l10n, e);
+      setState(() => _pendingVoiceChannelId = null);
       messenger.showSnackBar(
         SnackBar(
           content: Text(message),
@@ -1274,7 +1288,7 @@ class _BetaHomeState extends State<_BetaHome> {
       ],
     ];
 
-    const headerTitle = _AppBarTitle();
+    const headerTitle = SizedBox.shrink();
 
     final bodyContent = LayoutBuilder(
       builder: (ctx, bodyConstraints) {
@@ -1491,19 +1505,6 @@ class _BetaHomeState extends State<_BetaHome> {
   }
 }
 
-/// App header title. The current channel is highlighted only in the
-/// channel tree and Voice Bar to avoid repeating the same badge in
-/// multiple places.
-class _AppBarTitle extends StatelessWidget {
-  const _AppBarTitle();
-
-  @override
-  Widget build(BuildContext context) {
-    final l10n = AppL10n.of(context);
-    return Text(l10n.appTitle);
-  }
-}
-
 /// 'Save bookmark' name-entry dialog. Owns its own
 /// TextEditingController via a StatefulWidget lifecycle so the
 /// dispose() runs cleanly at unmount time (after the route pop