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/db/conversations.ts

@@ -2,7 +2,7 @@ import type Database from "bun:sqlite";
 
 import { desc, eq } from "drizzle-orm";
 
-import type { Conversation, Message } from "../../shared/api";
+import type { Conversation, Message, UpdateConversationRequest } from "../../shared/api";
 
 import { paginateQuery, wrap } from "./connection";
 import { conversations, messages, models } from "./schema";
@@ -150,6 +150,33 @@ export function listMessages(
   });
 }
 
+export function updateConversation(
+  raw: Database,
+  id: string,
+  data: UpdateConversationRequest,
+): { conversation: Conversation } | { error: string; status: number } {
+  const db = wrap(raw);
+  const existing = db.select().from(conversations).where(eq(conversations.id, id)).get();
+  if (!existing) return { error: "会话不存在", status: 404 };
+
+  const updates: { modelId?: string; title?: string; updatedAt: string } = { updatedAt: new Date().toISOString() };
+
+  if (data.modelId !== undefined) {
+    const model = db.select().from(models).where(eq(models.id, data.modelId)).get();
+    if (!model) return { error: "模型不存在", status: 400 };
+    updates.modelId = data.modelId;
+  }
+
+  if (data.title !== undefined) {
+    updates.title = data.title;
+  }
+
+  db.update(conversations).set(updates).where(eq(conversations.id, id)).run();
+
+  const row = db.select().from(conversations).where(eq(conversations.id, id)).get();
+  return { conversation: toConversation(row!) };
+}
+
 export function updateConversationTimestamp(raw: Database, id: string): void {
   const db = wrap(raw);
   db.update(conversations).set({ updatedAt: new Date().toISOString() }).where(eq(conversations.id, id)).run();