feat: stdio MCP wrapper + Windows Run-key autostart fallback (v1.0.1)

Two production-readiness fixes so colleagues can install cleanly:

1. Plugin's MCP server now spawns `claude-mailbox mcp-stdio`, a small
   stdio MCP wrapper that proxies tool calls to the daemon's REST API.
   Claude Code does not support env-var substitution in HTTP MCP `url`
   fields (issue #46889), so the wrapper is the only way to make the
   daemon URL configurable per machine via CLAUDE_MAILBOX_URL.

2. Windows `install-autostart` now falls back from `schtasks /Create`
   to an HKCU\Software\Microsoft\Windows\CurrentVersion\Run entry
   when Group Policy blocks the Scheduled Task path. Both modes are
   per-user, no admin, persist across logoffs. The chosen mode is
   recorded in ~/.claude-mailbox/autostart-mode so status/start/stop/
   uninstall-autostart pick the right cleanup path.

Also bumps the npm version to 1.0.1 to align with the published 1.0.0
plus this patch.

README.md

@@ -127,7 +127,7 @@ claude-mailbox uninstall-autostart [--purge]
 
 | Platform | Default mechanism | `--service` mechanism |
 |---|---|---|
-| Windows | Scheduled Task at logon (no admin) | Windows Service (admin, via `node-windows`) |
+| Windows | Scheduled Task at logon (no admin); falls back to HKCU Run-key if Group Policy blocks schtasks | Windows Service (admin, via `node-windows`) |
 | macOS | launchd LaunchAgent in `~/Library/LaunchAgents/` | n/a |
 | Linux | systemd `--user` unit in `~/.config/systemd/user/` | n/a |