feat: 聊天室模型选择器 + 会话更新 API + 消息部件重构

- 新增 PATCH /api/projects/:id/conversations/:cid 端点，支持更新 modelId 和 title
- 聊天面板新增模型选择下拉框，切换模型自动持久化
- 新建会话时传入默认文本模型 modelId
- 将 ToolCallCard 拆分为 ReasoningPart / TextPart / ToolPart 独立部件
- ToolPart 增加流式状态图标、折叠面板自动展开、错误详情展示
- ReasoningPart 增加思考中/思考完成状态指示
- 补充 PATCH 端点测试：更新成功、跨项目 403、不存在 404、无效 modelId 400

src/web/hooks/use-conversations.ts

@@ -3,6 +3,7 @@ import type {
   ConversationListResponse,
   ConversationResponse,
   MessageListResponse,
+  UpdateConversationRequest,
 } from "../../shared/api";
 
 import { handleResponse, handleVoidResponse } from "../utils/api";
@@ -43,3 +44,16 @@ export async function fetchMessages(projectId: string, conversationId: string):
   }
   return response.json() as Promise<MessageListResponse>;
 }
+
+export async function updateConversation(
+  projectId: string,
+  conversationId: string,
+  data: UpdateConversationRequest,
+): Promise<Conversation> {
+  const response = await fetch(`/api/projects/${projectId}/conversations/${conversationId}`, {
+    body: JSON.stringify(data),
+    headers: { "Content-Type": "application/json" },
+    method: "PATCH",
+  });
+  return handleResponse(response, (data) => (data as ConversationResponse).conversation);
+}