feat: add canonical state handoff ledger (#494)

Add templates, validators, and documentation for discussion/issue/PR state
comments and final-report next-action handoff fields. Wire enforcement into
assess_final_report_validator across all workflow task kinds.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

docs/llm-workflow-runbooks.md

@@ -830,6 +830,21 @@ scripts/release-tag v0.4.0 --notes-file /tmp/release-notes.md --push
 - [`credential-isolation.md`](credential-isolation.md) — credential handling.
 - [`release-workflows.md`](release-workflows.md) — release/merge workflow.
 - [`../README.md`](../README.md) — canonical config, thin launchers, the menu.
+- [`state-handoff-ledger.md`](state-handoff-ledger.md) — canonical state comments and next-action handoff (#494).
+
+## Canonical state handoff ledger (#494)
+
+Gitea comments and final reports must make continuation obvious without chat
+history. See [`state-handoff-ledger.md`](state-handoff-ledger.md) for:
+
+- discussion → issue → PR → review → merge → reconcile lifecycle
+- templates for discussion, issue, PR, and queue-controller state comments
+- final-report requirements: Current status, Next actor, Next action, Next prompt
+- queue-controller priority order and discussion ≥5-comment rule (urgent/trivial
+  exceptions)
+
+Helpers live in `state_handoff_ledger.py`; final-report enforcement is wired
+through `assess_final_report_validator`.
 
 ## PR-only queue cleanup mode (#390)