feat(briefing): stall watchdog + pull-to-refresh; chat attaches to in-flight streams

Briefing chat now uses the same StreamIterator + 45s per-event timeout
as the main chat provider, so a dropped SSE socket no longer leaves
isBriefingStreaming stuck true. Adds refreshMessages() that unfreezes
state when the server-side message is complete, wired to a new
pull-to-refresh gesture and the app lifecycle-resume hook.

Chat provider gains attachToGeneration() — safe to call unconditionally
on screen init, so landing on a conversation that's already mid-stream
(e.g. the /news discuss button, which now creates a conv and auto-kicks
generation server-side) picks up live tokens instead of freezing on the
placeholder.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/screens/briefing/briefing_screen.dart

@@ -41,7 +41,14 @@ class _BriefingScreenState extends ConsumerState<BriefingScreen>
 
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
+    final wasBackground = !_appInForeground;
     _appInForeground = state == AppLifecycleState.resumed;
+    // On resume, force a message refresh. This also unfreezes a stuck
+    // streaming state if the SSE socket died while the app was backgrounded
+    // — silentRefresh won't do that because it guards on isStreaming.
+    if (_appInForeground && wasBackground && mounted) {
+      ref.read(briefingProvider.notifier).refreshMessages();
+    }
   }
 
   void _pollSilently() {
@@ -51,6 +58,18 @@ class _BriefingScreenState extends ConsumerState<BriefingScreen>
     ref.read(briefingProvider.notifier).silentRefresh();
   }
 
+  Future<void> _pullToRefresh() async {
+    try {
+      await ref.read(briefingProvider.notifier).refreshMessages();
+    } catch (_) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Could not refresh.')),
+        );
+      }
+    }
+  }
+
   @override
   void dispose() {
     _pollTimer?.cancel();
@@ -250,9 +269,14 @@ class _BriefingScreenState extends ConsumerState<BriefingScreen>
           return Column(
             children: [
               Expanded(
-                child: CustomScrollView(
-                  controller: _scrollController,
-                  slivers: [
+                child: RefreshIndicator(
+                  onRefresh: _pullToRefresh,
+                  child: CustomScrollView(
+                    controller: _scrollController,
+                    // AlwaysScrollable so pull-to-refresh fires even when
+                    // the briefing is empty or shorter than the viewport.
+                    physics: const AlwaysScrollableScrollPhysics(),
+                    slivers: [
                     if (conv.messages.isEmpty)
                       SliverFillRemaining(
                         child: Center(
@@ -293,7 +317,8 @@ class _BriefingScreenState extends ConsumerState<BriefingScreen>
                           },
                         ),
                       ),
-                  ],
+                    ],
+                  ),
                 ),
               ),
 

lib/screens/chat/chat_screen.dart

@@ -44,6 +44,16 @@ class _ChatScreenState extends ConsumerState<ChatScreen>
   void initState() {
     super.initState();
     WidgetsBinding.instance.addObserver(this);
+    // If we land on a conversation whose last assistant message is already
+    // mid-stream (e.g. the /news discuss button creates a conv and
+    // auto-kicks generation), attach to the running stream so the user sees
+    // live tokens instead of a frozen placeholder.
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!mounted) return;
+      ref
+          .read(messagesProvider(widget.conversationId).notifier)
+          .attachToGeneration();
+    });
   }
 
   @override