feat(ui): adaptive 3-panel layout, chat panel switching, audio metering fix

- Add responsive breakpoints (compact <600, medium 600-1023, expanded >=1024)
- Add ViewportInfo InheritedWidget for layout-aware descendants
- Add inline ChatPanel (380dp right column) for expanded desktop layout
- Add channel right-click context menu with Chat option for in-place switching
- Add per-target draft persistence via restoredDraft/onDraftChanged callbacks
- Fix header chat button to switch to current voice channel when panel open
- Fix close = dismiss (preserves last target and draft for reopen)
- Add unread dot indicator on channel tiles when chat is closed
- Fix audio regression: decimate dBFS computation to every 3rd callback (~31 Hz)
  to avoid buffer underruns on macOS CoreAudio real-time thread
- Add tools/build-macos.sh release build script (7-step process)
- Add chat panel switching implementation plan and 3-panel design spec

Tests: 183 passed, 2 skipped. Flutter analyze clean.

apps/chanora_flutter/lib/widgets/chat_views.dart

@@ -2,6 +2,7 @@ import 'dart:async' show unawaited;
 
 import 'package:flutter/material.dart';
 
+import '../design/breakpoints.dart';
 import '../l10n/generated/app_localizations.dart';
 import '../services/channel_spacer.dart';
 import '../services/link_trust_service.dart';
@@ -13,7 +14,6 @@ import 'bbcode_text.dart';
 const double _chatSidebarTileExtent = 92;
 const double _chatSidebarCompactTileExtent = 76;
 const double _chatSidebarCompactHeight = 84;
-const double _chatMobileBreakpoint = 600;
 
 /// One chat/activity message shown in the chat hub.
 class ChatEntry {
@@ -616,7 +616,7 @@ class _ChatPageState extends State<ChatPage> {
     final currentChannelId = _currentChannelId;
     final channelName = snapshotChannelName(snapshot, currentChannelId);
     final l10n = AppL10n.of(context);
-    final detail = _ChatDetailView(
+    final detail = ChatDetailView(
       target: _selectedTarget,
       clientName: _selectedClientName,
       snapshot: snapshot,
@@ -641,7 +641,7 @@ class _ChatPageState extends State<ChatPage> {
       body: LayoutBuilder(
         builder: (context, constraints) {
           final sidebar = _ChatSidebar(
-            compact: constraints.maxWidth < _chatMobileBreakpoint,
+            compact: constraints.maxWidth < ChanoraBreakpoints.medium,
             selectedTarget: _selectedTarget,
             privateChats: _privateChats,
             onSelect: _selectTarget,
@@ -650,7 +650,7 @@ class _ChatPageState extends State<ChatPage> {
               _selectTarget(rust.BridgeMessageTarget.client(id), name: name);
             }),
           );
-          if (constraints.maxWidth < _chatMobileBreakpoint) {
+          if (constraints.maxWidth < ChanoraBreakpoints.medium) {
             return Column(
               children: [
                 sidebar,
@@ -1050,8 +1050,11 @@ class _ChannelGroup extends StatelessWidget {
   }
 }
 
-class _ChatDetailView extends StatefulWidget {
-  const _ChatDetailView({
+/// Detail view for a single chat target, including message history and input.
+class ChatDetailView extends StatefulWidget {
+  /// Construct a chat detail view.
+  const ChatDetailView({
+    super.key,
     required this.target,
     required this.clientName,
     required this.snapshot,
@@ -1059,21 +1062,50 @@ class _ChatDetailView extends StatefulWidget {
     required this.currentChannelId,
     required this.channelName,
     this.onTs3ServerLink,
+    this.headerTrailing,
+    this.messageMaxWidth,
+    this.restoredDraft,
+    this.onDraftChanged,
   });
 
+  /// Chat target displayed by this detail view.
   final rust.BridgeMessageTarget target;
+
+  /// Client display name for direct-message and poke targets.
   final String clientName;
+
+  /// Latest TeamSpeak snapshot.
   final rust.BridgeSnapshot snapshot;
+
+  /// Backing message list. Self-sent messages are appended here.
   final List<ChatEntry> messages;
+
+  /// Current voice channel id for channel-chat send gating.
   final BigInt? currentChannelId;
+
+  /// Current voice channel name for labels and placeholders.
   final String channelName;
+
+  /// Handle TeamSpeak server links embedded in chat messages.
   final Ts3ServerLinkHandler? onTs3ServerLink;
 
+  /// Optional widget shown at the trailing edge of the header.
+  final Widget? headerTrailing;
+
+  /// Optional max width for message content.
+  final double? messageMaxWidth;
+
+  /// External draft text to restore when the widget initializes or the target changes.
+  final String? restoredDraft;
+
+  /// Called with the current draft text whenever the target changes or the widget is about to be replaced.
+  final ValueChanged<String>? onDraftChanged;
+
   @override
-  State<_ChatDetailView> createState() => _ChatDetailViewState();
+  State<ChatDetailView> createState() => _ChatDetailViewState();
 }
 
-class _ChatDetailViewState extends State<_ChatDetailView> {
+class _ChatDetailViewState extends State<ChatDetailView> {
   final _textCtl = TextEditingController();
   final _scrollCtl = ScrollController();
   int _lastRenderedMessageCount = -1;
@@ -1100,8 +1132,31 @@ class _ChatDetailViewState extends State<_ChatDetailView> {
     clientName: widget.clientName,
   );
 
+  @override
+  void initState() {
+    super.initState();
+    if (widget.restoredDraft != null && widget.restoredDraft!.isNotEmpty) {
+      _textCtl.text = widget.restoredDraft!;
+    }
+  }
+
+  @override
+  void didUpdateWidget(covariant ChatDetailView oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    if (oldWidget.target != widget.target) {
+      if (oldWidget.onDraftChanged != null && _textCtl.text.isNotEmpty) {
+        oldWidget.onDraftChanged!(_textCtl.text);
+      }
+      _textCtl.text = widget.restoredDraft ?? '';
+      _lastRenderedTarget = null;
+    }
+  }
+
   @override
   void dispose() {
+    if (widget.onDraftChanged != null && _textCtl.text.isNotEmpty) {
+      widget.onDraftChanged!(_textCtl.text);
+    }
     _textCtl.dispose();
     _scrollCtl.dispose();
     super.dispose();
@@ -1176,7 +1231,12 @@ class _ChatDetailViewState extends State<_ChatDetailView> {
               bottom: BorderSide(color: theme.colorScheme.outlineVariant),
             ),
           ),
-          child: Text(_title, style: theme.textTheme.titleMedium),
+          child: Row(
+            children: [
+              Expanded(child: Text(_title, style: theme.textTheme.titleMedium)),
+              if (widget.headerTrailing != null) widget.headerTrailing!,
+            ],
+          ),
         ),
         Expanded(
           child: msgs.isEmpty
@@ -1216,9 +1276,16 @@ class _ChatDetailViewState extends State<_ChatDetailView> {
                   controller: _scrollCtl,
                   padding: const EdgeInsets.symmetric(vertical: 8),
                   itemCount: msgs.length,
-                  itemBuilder: (_, i) => _MessageBubble(
-                    entry: msgs[i],
-                    onTs3ServerLink: widget.onTs3ServerLink,
+                  itemBuilder: (_, i) => Center(
+                    child: ConstrainedBox(
+                      constraints: BoxConstraints(
+                        maxWidth: widget.messageMaxWidth ?? double.infinity,
+                      ),
+                      child: _MessageBubble(
+                        entry: msgs[i],
+                        onTs3ServerLink: widget.onTs3ServerLink,
+                      ),
+                    ),
                   ),
                 ),
         ),