EINTR errors in file watcher cause MCP initialization timeout

## Summary

MCP server initialization times out due to unhandled `EINTR` (interrupted system call) errors in the bundled Node.js CLI's file watcher. This causes sessions to crash and enter a timeout/recovery loop.

## Environment

- **OS**: macOS 15.2 (Darwin 25.2.0)
- **Python**: 3.13
- **SDK version**: Latest (installed via pip)
- **MCP tools registered**: 68 custom tools

## Error logs

```
Exception: Control request timeout: initialize

This error originated either by throwing inside of an async function without a catch block,
or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason:
Error: EINTR: interrupted system call, watch '/var/folders/h4/.../T/...-IBTOOLD-IN.QnhTSAefXh'
at watch (unknown)
at new FSWatcher (node:fs:29:31)
at watch (node:fs:296:23)
```

## Impact

- Every session eventually hits the 60-second initialization timeout
- Sessions enter an infinite timeout → recovery → timeout loop
- The application becomes unusable for multi-turn conversations

## Root cause analysis

The bundled CLI subprocess uses file watchers for IPC. When a system signal interrupts the `watch()` syscall, Node.js throws an `EINTR` error. This error is not caught/retried, causing the initialization to hang until it times out.

## Expected behavior

`EINTR` is a standard Unix signal indicating a syscall was interrupted and should be retried. The file watcher should:
1. Catch `EINTR` errors
2. Retry the watch operation
3. Not propagate the error up as a fatal failure

## Workaround

Setting `CLAUDE_CODE_STREAM_CLOSE_TIMEOUT=180000` (3 minutes) gives more time for initialization to eventually succeed, but doesn't fix the underlying issue.

## Reproduction

1. Create an MCP server with ~50+ tools
2. Use `ClaudeSDKClient` in a long-running server process
3. Send multiple messages over time
4. Observe `Control request timeout: initialize` errors in logs