fix(ui): address PR #30 review findings

- ViewportInfo.updateShouldNotify: compare layoutClass only
  (not width/height), avoiding unnecessary rebuilds on every
  resize frame within the same layout class.
- ChatPanel: use BorderDirectional(start:) for RTL support.
- ChatPanel: localize 'Close chat' tooltip via AppL10n.chatCloseAction.
- Inline panel snackbar: localize via AppL10n.chatPanelCollapsedHint.
  New en/zh ARB entries added.
- _saveCurrentDraft(): removed — it was a self-assignment no-op.
  Draft persistence relies on ChatDetailView's didUpdateWidget
  (fires onDraftChanged on target switch) and dispose (fires on
  panel tear-down), both of which already populate _chatDrafts
  correctly without an explicit save call.
- _handleInlineChatViewport layout snackbar: use AppL10n.
- Audio level-meter: switch from callback-count (% 3) to time-based
  gating (std::time::Duration::from_millis(33)), robust to cpal
  buffer-size or sample-rate changes. Remove level_decimation_counter.
- chat_panel_test.dart: add AppL10n.localizationsDelegates so the
  test resolves l10n keys.

Tests: 183 passed, 2 skipped. Dart analyze clean.
cargo test -p chanora_audio --lib: 125 passed.

apps/chanora_flutter/lib/design/viewport_info.dart

@@ -57,8 +57,11 @@ class ViewportInfo extends InheritedWidget {
   bool get isWide => !isCompact;
 
   @override
-  bool updateShouldNotify(ViewportInfo old) =>
-      layoutClass != old.layoutClass ||
-      width != old.width ||
-      height != old.height;
+  bool updateShouldNotify(ViewportInfo old) => layoutClass != old.layoutClass;
+  // NOTE: width/height changes within the same layout class do NOT trigger
+  // notification. Dependents who genuinely need pixel-level dimensions
+  // (rare — most layouts should switch on layoutClass) must use a local
+  // LayoutBuilder. Notifying on every pixel would rebuild every dependent
+  // on every resize frame, which is the exact pessimisation this
+  // InheritedWidget exists to avoid.
 }

apps/chanora_flutter/lib/l10n/app_en.arb

@@ -46,6 +46,7 @@
   "retryAction": "Retry",
   "chatAction": "Chat",
   "chatCloseAction": "Close chat",
+  "chatPanelCollapsedHint": "Tap the chat button to continue your conversation",
   "chatNewPrivateAction": "New private chat",
   "chatSearchClientsHint": "Search clients...",
   "chatDirectMessageAction": "Private message",

apps/chanora_flutter/lib/l10n/app_zh.arb

@@ -39,6 +39,7 @@
   "retryAction": "重试",
   "chatAction": "聊天",
   "chatCloseAction": "关闭聊天",
+  "chatPanelCollapsedHint": "点击聊天按钮以继续对话",
   "chatNewPrivateAction": "新建私聊",
   "chatSearchClientsHint": "搜索用户...",
   "chatDirectMessageAction": "私聊",

apps/chanora_flutter/lib/l10n/generated/app_localizations.dart

@@ -307,6 +307,12 @@ abstract class AppL10n {
   /// **'Close chat'**
   String get chatCloseAction;
 
+  /// No description provided for @chatPanelCollapsedHint.
+  ///
+  /// In en, this message translates to:
+  /// **'Tap the chat button to continue your conversation'**
+  String get chatPanelCollapsedHint;
+
   /// No description provided for @chatNewPrivateAction.
   ///
   /// In en, this message translates to:

apps/chanora_flutter/lib/l10n/generated/app_localizations_en.dart

@@ -123,6 +123,10 @@ class AppL10nEn extends AppL10n {
   @override
   String get chatCloseAction => 'Close chat';
 
+  @override
+  String get chatPanelCollapsedHint =>
+      'Tap the chat button to continue your conversation';
+
   @override
   String get chatNewPrivateAction => 'New private chat';
 

apps/chanora_flutter/lib/l10n/generated/app_localizations_zh.dart

@@ -120,6 +120,9 @@ class AppL10nZh extends AppL10n {
   @override
   String get chatCloseAction => '关闭聊天';
 
+  @override
+  String get chatPanelCollapsedHint => '点击聊天按钮以继续对话';
+
   @override
   String get chatNewPrivateAction => '新建私聊';
 

apps/chanora_flutter/lib/main.dart

@@ -1673,17 +1673,18 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
     };
   }
 
-  /// Saves the current draft text for the current inline chat target.
-  void _saveCurrentDraft() {
-    // Drafts are continuously saved via onDraftChanged callback in Task 4.
-    // This method exists as an explicit save point.
-    final target = _inlineChatTarget;
-    if (target == null) return;
-    final key = _draftKeyForTarget(target);
-    if (_chatDrafts.containsKey(key)) {
-      _chatDrafts[key] = _chatDrafts[key] ?? '';
-    }
-  }
+  /// Returns the current draft text for the inline chat target, or null
+  /// if no draft has been stored.
+  ///
+  /// Draft persistence relies on [ChatDetailView]'s own lifecycle:
+  /// `didUpdateWidget` flushes the outgoing target's draft via
+  /// `onDraftChanged` when the parent rebuilds with a new target, and
+  /// `dispose` flushes the final draft when the panel is torn down
+  /// (e.g. on [_closeInlineChat]). Both paths feed
+  /// [_chatDrafts] without requiring an explicit save call from this
+  /// class.
+  String? _currentDraftFor(rust.BridgeMessageTarget target) =>
+      _chatDrafts[_draftKeyForTarget(target)];
 
   Future<void> _onOpenChat({
     rust.BridgeMessageTarget? target,
@@ -1722,8 +1723,9 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
         layoutClassFromWidth(MediaQuery.sizeOf(context).width) ==
         LayoutClass.expanded;
     if (isExpanded) {
+      // Outgoing draft is preserved by ChatDetailView.didUpdateWidget,
+      // which fires onDraftChanged with the old target's text on rebuild.
       setState(() {
-        _saveCurrentDraft();
         _chatUnread = 0;
         _chatOpen = true;
         _inlineChatTarget = newTarget;
@@ -1754,8 +1756,10 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
   }
 
   void _closeInlineChat() {
+    // Final draft for the dismissed target is preserved by
+    // ChatDetailView.dispose, which fires onDraftChanged when the panel
+    // is removed from the tree on the next rebuild.
     setState(() {
-      _saveCurrentDraft();
       _lastDismissedTarget = _inlineChatTarget;
       _lastDismissedClientName = _inlineChatClientName;
       _chatOpen = false;
@@ -1788,8 +1792,8 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
     WidgetsBinding.instance.addPostFrameCallback((_) {
       if (!mounted || _inlineChatTarget == null) return;
       ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(
-          content: Text('Tap the chat button to continue your conversation'),
+        SnackBar(
+          content: Text(AppL10n.of(context).chatPanelCollapsedHint),
         ),
       );
     });
@@ -2654,10 +2658,9 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
                                 snapshot: _snapshot!,
                                 target: inlineChatTarget,
                                 clientName: _inlineChatClientName,
-                                restoredDraft:
-                                    _chatDrafts[_draftKeyForTarget(
-                                      inlineChatTarget,
-                                    )],
+                                restoredDraft: _currentDraftFor(
+                                  inlineChatTarget,
+                                ),
                                 onDraftChanged: (text) {
                                   final draftKey = _draftKeyForTarget(
                                     inlineChatTarget,

apps/chanora_flutter/lib/widgets/chat_panel.dart

@@ -3,6 +3,7 @@
 import 'package:flutter/material.dart';
 
 import '../design/breakpoints.dart';
+import '../l10n/generated/app_localizations.dart';
 import '../services/snapshot_state_mapper.dart';
 import '../services/ts3_server_link.dart';
 import '../src/rust/api.dart' as rust;
@@ -51,14 +52,15 @@ class ChatPanel extends StatelessWidget {
   Widget build(BuildContext context) {
     final currentChannelId = ownClientSnapshotState(snapshot)?.channelId;
     final channelName = snapshotChannelName(snapshot, currentChannelId);
+    final l10n = AppL10n.of(context);
 
     return SizedBox(
       width: ChanoraBreakpoints.chatPanelWidth,
       child: DecoratedBox(
         decoration: BoxDecoration(
           color: Theme.of(context).colorScheme.surface,
-          border: Border(
-            left: BorderSide(
+          border: BorderDirectional(
+            start: BorderSide(
               color: Theme.of(context).colorScheme.outlineVariant,
             ),
           ),
@@ -75,7 +77,7 @@ class ChatPanel extends StatelessWidget {
           onDraftChanged: onDraftChanged,
           messageMaxWidth: 500,
           headerTrailing: IconButton(
-            tooltip: 'Close chat',
+            tooltip: l10n.chatCloseAction,
             icon: const Icon(Icons.close),
             onPressed: onClose,
           ),

apps/chanora_flutter/test/widgets/chat_panel_test.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import 'package:chanora_flutter/l10n/generated/app_localizations.dart';
 import 'package:chanora_flutter/src/rust/api.dart' as rust;
 import 'package:chanora_flutter/widgets/chat_panel.dart';
 import 'package:chanora_flutter/widgets/chat_views.dart';
@@ -55,6 +56,8 @@ void main() {
 
     await tester.pumpWidget(
       MaterialApp(
+        localizationsDelegates: AppL10n.localizationsDelegates,
+        supportedLocales: AppL10n.supportedLocales,
         home: Scaffold(
           body: ChatPanel(
             messages: messages,
@@ -87,6 +90,8 @@ void main() {
       required String? restoredDraft,
     }) {
       return MaterialApp(
+        localizationsDelegates: AppL10n.localizationsDelegates,
+        supportedLocales: AppL10n.supportedLocales,
         home: Scaffold(
           body: ChatDetailView(
             messages: messages,