Persist publish-block reasons on git push readiness failures #88
Description
Goal
When publish or commit-and-push work is blocked by git/remote readiness checks, store a structured block reason so the system can distinguish infra constraints from code failures.
Success Criteria
- Git publish readiness failures emit a stable blocker code and short reason into the task outcome.
- The recorded reason is available to backlog grooming and retry/quarantine logic.
- Publish-blocked tasks no longer appear as generic debugging blocks without actionable cause data.
Constraints
- Prefer minimal diffs