test(server): 补充 checkpoints/mcp/sse/adapter 测试

- 新增 checkpoints.test.ts: 29 个测试覆盖 Checkpoint 管理 API
- 新增 mcp.test.ts: 15 个测试覆盖 MCP 服务器管理 API
- 扩展 sse.test.ts: 添加 handleSSE 路由测试
- 扩展 adapter.test.ts: 添加 cancelProcessing, getContextUsage,
  compressContext, processMessage 测试

覆盖率提升: 60% -> 80.82%
测试数量: 288 -> 344

packages/server/tests/unit/sse.test.ts

@@ -5,17 +5,19 @@
  */
 
 import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { Hono } from 'hono';
 
 // Mock dependencies before imports
 const mockExists = vi.fn();
+const mockSessionManager = {
+  exists: mockExists,
+};
 
 vi.mock('../../src/session/manager.js', () => ({
-  getSessionManager: vi.fn(() => ({
-    exists: mockExists,
-  })),
+  getSessionManager: vi.fn(() => mockSessionManager),
 }));
 
-// Import after mocking - note: some functions are internal and not testable directly
+// Import after mocking
 import {
   emitEvent,
   broadcastEvent,
@@ -24,6 +26,7 @@ import {
   emitProgressEvent,
   emitFileChangeEvent,
   getSSEStats,
+  handleSSE,
 } from '../../src/sse.js';
 
 describe('SSE Handler', () => {
@@ -138,4 +141,34 @@ describe('SSE Handler', () => {
       expect(typeof stats.subscribers).toBe('number');
     });
   });
+
+  describe('handleSSE - SSE 路由处理', () => {
+    it('会话不存在时返回 404', async () => {
+      mockExists.mockReturnValue(false);
+
+      const app = new Hono();
+      app.get('/api/sessions/:id/events', handleSSE);
+
+      const res = await app.request('/api/sessions/non-existent/events');
+      const json = await res.json();
+
+      expect(res.status).toBe(404);
+      expect(json.success).toBe(false);
+      expect(json.error).toBe('Session not found');
+    });
+
+    it('会话存在时返回 SSE 流响应', async () => {
+      mockExists.mockReturnValue(true);
+
+      const app = new Hono();
+      app.get('/api/sessions/:id/events', handleSSE);
+
+      const res = await app.request('/api/sessions/valid-session/events');
+
+      // SSE 流应该返回 200 状态码
+      expect(res.status).toBe(200);
+      // Content-Type 应该是 text/event-stream
+      expect(res.headers.get('content-type')).toContain('text/event-stream');
+    });
+  });
 });