Fix macOS Cmd+; global hotkey never firing

The LaunchAgent runs `jcode setup-hotkey --listen-macos-hotkey`, but that was
dispatched on a tokio worker thread after the runtime was built, and the
listener just blocked on `recv()`. global-hotkey on macOS delivers Carbon
`RegisterEventHotKey` events through the *main thread's* Core Foundation run
loop, which was never created or pumped, so Cmd+; silently did nothing.

- Intercept `setup-hotkey --listen-macos-hotkey` in main() before the tokio
  runtime is built, so the listener runs on the real main thread.
- Pump the CF run loop (CFRunLoopRunInMode) in the listener and drain hotkey
  events via try_recv, so presses actually fire and launch jcode.
- Add a tiny CoreFoundation binding (no new dependency) and unit tests for the
  arg interception.

Apple Terminal launch path itself was already correct (osascript do script).