feat: show tool status notifications in chat during generation

Parse SSE `status` events alongside `chunk` events and display the
status text next to the spinner while the assistant is generating.
Previously the Android app discarded all non-chunk SSE events.

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

lib/providers/chat_provider.dart

@@ -2,6 +2,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../data/models/conversation.dart';
 import '../data/models/message.dart';
+import '../data/repositories/chat_repository.dart';
 import 'api_client_provider.dart';
 
 // Separate NotifierProvider.family so UI re-builds immediately when streaming starts/stops.
@@ -18,6 +19,20 @@ class _IsStreamingNotifier extends Notifier<bool> {
   bool build() => false;
 }
 
+// Tracks the current tool status text during generation (empty = no status).
+final streamingStatusProvider =
+    NotifierProvider.family<_StreamingStatusNotifier, String, int>(
+  (convId) => _StreamingStatusNotifier(convId),
+);
+
+class _StreamingStatusNotifier extends Notifier<String> {
+  // ignore: avoid_unused_constructor_parameters
+  _StreamingStatusNotifier(int convId);
+
+  @override
+  String build() => '';
+}
+
 final conversationsProvider =
     AsyncNotifierProvider<ConversationsNotifier, List<Conversation>>(
         ConversationsNotifier.new);
@@ -103,12 +118,19 @@ class MessagesNotifier extends AsyncNotifier<List<Message>> {
     // ── Step 2: Stream the response (best effort — silent on failure). ──
     bool streamedContent = false;
     try {
-      await for (final chunk in repo.streamGeneration(convId)) {
-        streamedContent = true;
-        final msgs = state.requireValue;
-        if (msgs.isEmpty) continue;
-        final updated = msgs.last.copyWith(content: msgs.last.content + chunk);
-        state = AsyncData([...msgs.sublist(0, msgs.length - 1), updated]);
+      await for (final event in repo.streamGeneration(convId)) {
+        if (event is ChatTextChunk) {
+          streamedContent = true;
+          ref.read(streamingStatusProvider(convId).notifier).state = '';
+          final msgs = state.requireValue;
+          if (msgs.isEmpty) continue;
+          final updated =
+              msgs.last.copyWith(content: msgs.last.content + event.text);
+          state = AsyncData([...msgs.sublist(0, msgs.length - 1), updated]);
+        } else if (event is ChatStatusUpdate) {
+          ref.read(streamingStatusProvider(convId).notifier).state =
+              event.status;
+        }
       }
     } catch (_) {
       // SSE failed — fall through to the polling reload below.
@@ -157,6 +179,7 @@ class MessagesNotifier extends AsyncNotifier<List<Message>> {
       }
     } finally {
       ref.read(isStreamingProvider(convId).notifier).state = false;
+      ref.read(streamingStatusProvider(convId).notifier).state = '';
     }
   }
 }