Three unguarded blocking calls caused CI to hang until the 60-min timeout:
- dagger query prune steps had no timeout; || true only catches errors, not hangs
- docker info (added in d905cd6) had no timeout if Docker socket is unresponsive
- until portfile loop in check-dagger spun forever if otel-receiver.py crashed
Fixes: timeout 120 on all dagger query prune calls, timeout 30 on docker info,
and a kill -0 process-alive guard on the portfile until loop with fallback.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>