Doctor checks spawned subprocesses (gh, opencode, sg) without timeouts,
causing the process to hang indefinitely if any binary was stuck.
The OS would then SIGKILL the process (exit code 137).
- Add spawnWithTimeout utility with 10s per-spawn timeout
- Add 30s overall doctor command timeout with graceful error message
- Update all doctor check subprocess calls to use timeouts
YeonGyu-Kim