feat: 重构为 Monorepo 架构并实现 HTTP Server

架构变更:
- 采用 pnpm workspaces 实现 Monorepo 结构
- 将现有代码迁移到 packages/core
- 新增 packages/server HTTP 服务层

Server 功能:
- REST API: 会话管理、工具管理、配置管理
- WebSocket: 实时双向通信支持
- SSE: 服务端事件推送
- Hono + Bun 作为运行时

API 端点:
- GET/POST /api/sessions - 会话 CRUD
- GET/POST /api/sessions/:id/messages - 消息管理
- GET /api/sessions/:id/events - SSE 事件流
- WS /api/ws/:sessionId - WebSocket 连接
- GET/POST /api/tools - 工具管理
- GET/PUT /api/config - 配置管理

packages/server/src/routes/sessions.ts

@@ -0,0 +1,178 @@
+/**
+ * Sessions API Routes
+ *
+ * 会话管理相关的 REST API
+ */
+
+import { Hono } from 'hono';
+import { getSessionManager } from '../session/manager.js';
+import { CreateSessionInputSchema, SendMessageInputSchema } from '../types.js';
+
+export const sessionsRouter = new Hono();
+
+const sessionManager = getSessionManager();
+
+/**
+ * GET /sessions - 列出所有会话
+ */
+sessionsRouter.get('/', (c) => {
+  const sessions = sessionManager.list();
+  return c.json({
+    success: true,
+    data: sessions,
+  });
+});
+
+/**
+ * POST /sessions - 创建新会话
+ */
+sessionsRouter.post('/', async (c) => {
+  try {
+    const body = await c.req.json();
+    const input = CreateSessionInputSchema.parse(body);
+    const session = sessionManager.create(input);
+
+    return c.json(
+      {
+        success: true,
+        data: session,
+      },
+      201
+    );
+  } catch (error) {
+    return c.json(
+      {
+        success: false,
+        error: error instanceof Error ? error.message : 'Invalid input',
+      },
+      400
+    );
+  }
+});
+
+/**
+ * GET /sessions/:id - 获取单个会话
+ */
+sessionsRouter.get('/:id', (c) => {
+  const id = c.req.param('id');
+  const session = sessionManager.get(id);
+
+  if (!session) {
+    return c.json(
+      {
+        success: false,
+        error: 'Session not found',
+      },
+      404
+    );
+  }
+
+  return c.json({
+    success: true,
+    data: session,
+  });
+});
+
+/**
+ * DELETE /sessions/:id - 删除会话
+ */
+sessionsRouter.delete('/:id', (c) => {
+  const id = c.req.param('id');
+
+  if (!sessionManager.exists(id)) {
+    return c.json(
+      {
+        success: false,
+        error: 'Session not found',
+      },
+      404
+    );
+  }
+
+  sessionManager.delete(id);
+
+  return c.json({
+    success: true,
+    message: 'Session deleted',
+  });
+});
+
+/**
+ * GET /sessions/:id/messages - 获取会话消息
+ */
+sessionsRouter.get('/:id/messages', (c) => {
+  const id = c.req.param('id');
+
+  if (!sessionManager.exists(id)) {
+    return c.json(
+      {
+        success: false,
+        error: 'Session not found',
+      },
+      404
+    );
+  }
+
+  const messages = sessionManager.getMessages(id);
+
+  return c.json({
+    success: true,
+    data: messages,
+  });
+});
+
+/**
+ * POST /sessions/:id/messages - 发送消息
+ *
+ * 注意: 这个端点仅用于添加消息记录。
+ * 实际的 AI 对话应该通过 WebSocket 进行。
+ */
+sessionsRouter.post('/:id/messages', async (c) => {
+  const id = c.req.param('id');
+
+  if (!sessionManager.exists(id)) {
+    return c.json(
+      {
+        success: false,
+        error: 'Session not found',
+      },
+      404
+    );
+  }
+
+  try {
+    const body = await c.req.json();
+    const input = SendMessageInputSchema.parse(body);
+
+    const message = sessionManager.addMessage(id, {
+      role: input.role,
+      content: input.content,
+    });
+
+    if (!message) {
+      return c.json(
+        {
+          success: false,
+          error: 'Failed to add message',
+        },
+        500
+      );
+    }
+
+    return c.json(
+      {
+        success: true,
+        data: message,
+      },
+      201
+    );
+  } catch (error) {
+    return c.json(
+      {
+        success: false,
+        error: error instanceof Error ? error.message : 'Invalid input',
+      },
+      400
+    );
+  }
+});