Require and validate Controller Handoff sections in workflow final reports

- Upgrade SKILL.md §K compact format to the issue #182 canonical field set
  (Task/Repo/Role/Identity/Issue-PR/Branch-SHA/Files/Validation/Mutations/
  Current status/Blockers/Next/Safety) plus role-specific field lists for
  review/merge, author, and queue/inventory tasks.
- Point the review-pr, merge-pr, and start-issue template handoff lines at
  the exactly-titled Controller Handoff section with their role fields.
- Add review_proofs.assess_controller_handoff(): reports without the exact
  section are 'missing' (downgraded), present-but-partial are 'incomplete'
  with the absent fields listed, and role extras are enforced per role.
- Add TestControllerHandoff (8 tests) including a SKILL.md doc-contract
  test so the documented requirement cannot silently rot.

The handoff supplements the full report; full-report validation rules are
unchanged.

Closes #182

Co-Authored-By: Claude Fable 5 <[email protected]>

skills/llm-project-workflow/templates/review-pr.md

@@ -65,7 +65,10 @@ Steps:
    - MCP-Profile: <profile name>
    - Eligibility: passed/failed
 
-Handoff: reviewer identity, PR author, scope verdict, checks + results, decision —
-formatted per SKILL.md §K (compact by default; long form if a merge happened
-or a gate blocked you); if you could not merge, name the exact gate.
+Handoff: end with a section titled exactly `Controller Handoff` per SKILL.md
+§K (compact by default; long form if a merge happened or a gate blocked you),
+including the review/merge role fields: Selected PR, Reviewer eligibility,
+Pinned reviewed head, Review decision, Merge result, Linked issue status,
+Cleanup status. If you could not merge, name the exact gate. Reports missing
+the handoff are downgraded (review_proofs.assess_controller_handoff).
 ```