Report sanitized revision readiness category

[Pigbibi]

Summary

• emit only a fixed Cloud Run Ready-condition category when no-traffic revision readiness fails
• retain fail-closed behavior and avoid logging raw condition reason, message, revision, service, or account data
• add regression coverage

Validation

• uv run --frozen --extra test python -m pytest -q tests/test_sync_cloud_run_env_workflow.py
• actionlint .github/workflows/sync-cloud-run-env.yml
• git diff --check