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/server/routes/chat/update.ts

@@ -0,0 +1,47 @@
+import type Database from "bun:sqlite";
+
+import type { RuntimeMode, UpdateConversationRequest } from "../../../shared/api";
+
+import { getConversation, updateConversation } from "../../db/conversations";
+import { createApiError, jsonResponse } from "../../helpers";
+import { validateIdParam } from "../../middleware";
+
+export async function handleUpdateConversation(req: Request, db: Database, mode: RuntimeMode): Promise<Response> {
+  const url = new URL(req.url);
+  const parts = url.pathname.split("/");
+  const projectId = parts[3];
+  const conversationId = parts[5];
+
+  const validatedProject = validateIdParam(projectId ?? "", mode);
+  if (validatedProject instanceof Response) return validatedProject;
+
+  const validatedConv = validateIdParam(conversationId ?? "", mode);
+  if (validatedConv instanceof Response) return validatedConv;
+
+  const existing = getConversation(db, validatedConv.id);
+  if ("error" in existing) {
+    return jsonResponse(createApiError(existing.error, existing.status), { mode, status: existing.status });
+  }
+
+  if (existing.conversation.projectId !== validatedProject.id) {
+    return jsonResponse(createApiError("会话不属于该项目", 403), { mode, status: 403 });
+  }
+
+  let body: UpdateConversationRequest;
+  try {
+    body = (await req.json()) as UpdateConversationRequest;
+  } catch {
+    return jsonResponse(createApiError("Invalid JSON body", 400), { mode, status: 400 });
+  }
+
+  if (body.modelId === undefined && body.title === undefined) {
+    return jsonResponse(createApiError("至少需要传 modelId 或 title", 400), { mode, status: 400 });
+  }
+
+  const result = updateConversation(db, validatedConv.id, body);
+  if ("error" in result) {
+    return jsonResponse(createApiError(result.error, result.status), { mode, status: result.status });
+  }
+
+  return jsonResponse({ conversation: result.conversation }, { mode });
+}