feat(chat): render tool-call chips and live peek status in mobile bubbles

The mobile app was receiving SSE status events but showing the peek text
only while the assistant bubble was empty — as soon as the first token
arrived, the status line was replaced by streaming content and any tool
calls fired mid-turn left no trace. Tool call SSE events were also being
dropped by the parser, and Message.fromJson never read the persisted
tool_calls array, so chips never rendered after reload either.

Parse tool_call SSE frames into a new ChatToolCall event, carry tool
calls on Message, and update the chat and briefing streaming loops to
append chips to the in-flight assistant message as they arrive. Rework
ChatMessageBubble to show a chip row + rolling peek status line above
any streamed text, matching the web ToolCallCard/status indicator
behaviour across chat, briefing, and briefing history surfaces.

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

lib/data/api/chat_api.dart

@@ -18,6 +18,15 @@ class ChatStatusUpdate extends ChatStreamEvent {
   ChatStatusUpdate(this.status);
 }
 
+/// A single tool call fired during generation. Mirrors the `tool_call` SSE
+/// event emitted by `generation_task.py` and the `tool_calls` array persisted
+/// on the assistant Message row — same shape either way so the UI can render
+/// live chips during streaming and re-render them from storage after reload.
+class ChatToolCall extends ChatStreamEvent {
+  final Map<String, dynamic> toolCall;
+  ChatToolCall(this.toolCall);
+}
+
 class ChatApi {
   final Dio _dio;
   const ChatApi(this._dio);
@@ -136,6 +145,14 @@ class ChatApi {
               } catch (_) {
                 // Ignore malformed status events
               }
+            } else if (currentEvent == 'tool_call') {
+              try {
+                final obj = json.decode(data) as Map<String, dynamic>;
+                final tc = obj['tool_call'];
+                if (tc is Map<String, dynamic>) yield ChatToolCall(tc);
+              } catch (_) {
+                // Ignore malformed tool_call events
+              }
             }
           } else if (line.isEmpty) {
             currentEvent = ''; // blank line = SSE event separator