[BUG] `--resume` session picker leaves FSWatcher handles open, preventing Ctrl+D exit

Bug Description

After using claude --resume with the interactive session picker, pressing Ctrl+D twice does not exit Claude Code. The process hangs and requires Ctrl+C to terminate.

Root Cause

9 FSWatcher handles remain active after the session picker closes, preventing the Node.js event loop from exiting on EOF (Ctrl+D).

> process._getActiveHandles().filter(h => h.constructor?.name === 'FSWatcher')
[ FSWatcher, FSWatcher, FSWatcher, FSWatcher, FSWatcher, FSWatcher, FSWatcher, FSWatcher, FSWatcher ]

Reproduction Steps

1. Start a new Claude Code session: claude
2. Send any message, then exit (Ctrl+D works fine)
3. Resume with session picker: claude --resume
4. Select a session from the picker
5. Press Ctrl+D twice
6. Expected: Claude Code exits
7. Actual: Process hangs, no response. Only Ctrl+C terminates it.

Working Scenarios

| Command | Ctrl+D Exit |
|---------|-------------|
| claude (new session) | ✓ Works |
| claude --continue | ✓ Works |
| claude --resume <session-id> | ✓ Works |
| claude --resume (picker UI) | ✗ Hangs |

Debug Log Analysis

When the issue occurs, debug logs show:

• Startup and plugin initialization complete
• No [REPL:mount] entry after session picker selection
• No keyboard/input events logged
• Process stuck between picker close and REPL mount

Normal session shows:

[keybindings] KeybindingSetup initialized
[REPL:mount] REPL mounted, disabled=false
...
[REPL:unmount] REPL unmounting

Hanging session shows only startup logs, then silence.

Environment

• OS: Windows 11 (cmd/Git Bash), macOS, WSL2 Ubuntu 24.04
• Claude Code versions: 2.1.9, 2.1.10, 2.1.11, 2.1.12 (all affected)
• Node.js versions: v20.x, v22.20.0 (all affected)
• Fresh install: Issue reproduces on fresh Claude Code installation

Workarounds

• Use /exit command instead of Ctrl+D
• Use claude --continue instead of --resume
• Specify session ID directly: claude --resume <session-id>

Related Issues

• #15210 - FSWatcher file descriptor leak (similar FSWatcher cleanup issue)