docs(sdk): document Nanobot teardown

docs/python-sdk.md

@@ -11,8 +11,8 @@ from nanobot import Nanobot
 
 
 async def main() -> None:
-    bot = Nanobot.from_config()
-    result = await bot.run("What time is it in Tokyo?")
+    async with Nanobot.from_config() as bot:
+        result = await bot.run("What time is it in Tokyo?")
     print(result.content)
 
 
@@ -21,6 +21,8 @@ asyncio.run(main())
 
 `Nanobot.from_config()` reuses your normal `~/.nanobot/config.json`, so the SDK follows the same provider, model, tools, and workspace defaults as the CLI unless you override them.
 
+Use `async with` when possible so MCP connections and background cleanup work are closed before the event loop exits. If you manage the instance manually, call `await bot.aclose()` in a `finally` block.
+
 ## Common Patterns
 
 ### Use a specific config or workspace
@@ -83,6 +85,15 @@ Run the agent once and return a `RunResult`.
 | `session_key` | `str` | `"sdk:default"` | Session identifier for conversation isolation. Different keys get independent history. |
 | `hooks` | `list[AgentHook] \| None` | `None` | Lifecycle hooks for this run only. |
 
+### `await bot.aclose()`
+
+Release resources held by the SDK instance, including MCP connections. The async context manager calls this automatically:
+
+```python
+async with Nanobot.from_config() as bot:
+    result = await bot.run("Summarize this repo")
+```
+
 ### `RunResult`
 
 | Field | Type | Description |