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/start-issue.md

@@ -42,7 +42,10 @@ Steps:
    - Self-review allowed: no
 9. Stop before review/merge — you are the author.
 
-Handoff: issue #, branch, worktree path, files changed, checks + results, PR URL —
-formatted as the compact Controller Handoff (SKILL.md §K; long form only on
-the high-risk triggers); Review line: "Review needed — PR is open".
+Handoff: end with a section titled exactly `Controller Handoff` per SKILL.md
+§K (compact; long form only on the high-risk triggers), including the author
+role fields: Selected issue, Claim/comment status, PR number opened, and an
+explicit "No review/merge:" confirmation — plus branch, worktree path, files
+changed, checks + results. Next line: "Review needed — PR is open". Reports
+missing the handoff are downgraded (review_proofs.assess_controller_handoff).
 ```