refactor(box): launch box runtime via the lbp CLI subcommand

Mirror the plugin runtime: box is now started through the same CLI entry
point (langbot_plugin.cli) instead of the box module directly.

- docker-compose.yaml: langbot_box command runs `langbot_plugin.cli ... box`
  (WebSocket is the default transport, no flag needed — matches `rt`).
- box/connector.py: both subprocess launch sites (_start_local_stdio and
  the Windows _start_subprocess_then_ws path) invoke
  `langbot_plugin.cli.__init__ box`, using `-s` for the stdio transport.
- docs/review: update stale `-m langbot_plugin.box[.server]` references.

Pairs with the SDK change that removes box's direct-launch entry points
(python -m langbot_plugin.box / .box.server) and the legacy --mode flag.

docs/review/box-architecture.md

@@ -142,7 +142,7 @@ BoxService
 
 管理与 Box Runtime 的通信连接：
 
-- **本地 stdio**: Unix/macOS 默认路径，fork `python -m langbot_plugin.box --port {port}` 子进程
+- **本地 stdio**: Unix/macOS 默认路径，fork `python -m langbot_plugin.cli.__init__ box -s --ws-control-port {port}` 子进程（与 plugin runtime 统一走 `lbp` CLI 入口）
 - **本地 subprocess + WS**: Windows 本地（asyncio ProactorEventLoop 不支持 stdio pipe）
 - **远程 WebSocket**: Docker 部署 / `box.runtime.endpoint` 显式配置时，连接 `ws://{host}:{port}/rpc/ws`
 - **同步等待**: `asyncio.Event` + `wait_for(timeout=30s)` 模式确认连接

docs/review/box-vs-plugin-runtime.md

@@ -75,7 +75,7 @@ else:
 ```
 connector._start_local_stdio()
   ├─ connected = asyncio.Event()
-  ├─ ctrl = StdioClientController(python, ['-m', 'langbot_plugin.box.server', '--port', N])
+  ├─ ctrl = StdioClientController(python, ['-m', 'langbot_plugin.cli.__init__', 'box', '-s', '--ws-control-port', N])
   ├─ _ctrl_task = create_task(ctrl.run(callback))
   │    callback:
   │      handler = Handler(connection)          ← 基础 Handler, 无 disconnect_callback