feat: 添加后台 Agent 执行和模型选择功能

- 新增 AgentManager 管理后台 Agent 生命周期
- Task 工具支持 run_in_background 参数实现后台执行
- Task 工具支持 model 参数选择 sonnet/opus/haiku 模型
- 新增 agent_output 工具查询后台 Agent 执行状态和结果
- 添加 AgentManager 和 AgentOutput 工具单元测试

package-lock.json

@@ -19,6 +19,7 @@
         "js-yaml": "^4.1.1",
         "ora": "^8.1.0",
         "tree-sitter-bash": "^0.25.1",
+        "uuid": "^13.0.0",
         "vscode-jsonrpc": "^8.2.1",
         "vscode-languageserver-protocol": "^3.17.5",
         "web-tree-sitter": "^0.25.10",
@@ -30,6 +31,7 @@
       "devDependencies": {
         "@types/js-yaml": "^4.0.9",
         "@types/node": "^22.0.0",
+        "@types/uuid": "^10.0.0",
         "@vitest/coverage-v8": "^4.0.15",
         "tsx": "^4.19.0",
         "typescript": "^5.6.0",
@@ -1354,6 +1356,13 @@
         "undici-types": "~6.21.0"
       }
     },
+    "node_modules/@types/uuid": {
+      "version": "10.0.0",
+      "resolved": "https://registry.npmjs.org/@types/uuid/-/uuid-10.0.0.tgz",
+      "integrity": "sha512-7gqG38EyHgyP1S+7+xomFtL+ZNHcKv6DwNaCZmJmo1vgMugyF3TCnXVg4t1uk89mLNwnLtnY3TpOpCOyp1/xHQ==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@vercel/oidc": {
       "version": "3.0.5",
       "resolved": "https://registry.npmjs.org/@vercel/oidc/-/oidc-3.0.5.tgz",
@@ -2882,6 +2891,19 @@
       "devOptional": true,
       "license": "MIT"
     },
+    "node_modules/uuid": {
+      "version": "13.0.0",
+      "resolved": "https://registry.npmjs.org/uuid/-/uuid-13.0.0.tgz",
+      "integrity": "sha512-XQegIaBTVUjSHliKqcnFqYypAd4S+WCYt5NIeRs6w/UAry7z8Y9j5ZwRRL4kzq9U3sD6v+85er9FvkEaBpji2w==",
+      "funding": [
+        "https://github.com/sponsors/broofa",
+        "https://github.com/sponsors/ctavan"
+      ],
+      "license": "MIT",
+      "bin": {
+        "uuid": "dist-node/bin/uuid"
+      }
+    },
     "node_modules/vite": {
       "version": "7.2.7",
       "resolved": "https://registry.npmjs.org/vite/-/vite-7.2.7.tgz",