feat(lease): guarded cleanup for obsolete reviewer comment leases (Closes #691)

Add fail-closed assessment and MCP tool for expired/superseded-head
comment-backed reviewer leases that lack a control-plane lease_id.

- assess_obsolete_reviewer_comment_lease_cleanup eligibility matrix
- diagnose classifications: foreign_active_current_head,
  foreign_expired_current_head, foreign_completed_superseded_head,
  foreign_expired_superseded_head, orphaned_owner_missing,
  ambiguous_conflicting_evidence
- gitea_cleanup_obsolete_reviewer_comment_lease with confirmation
  CLEANUP OBSOLETE REVIEWER LEASE <n> and controller_recovery_authorized
- preserve audit history via append-only phase=released marker
- never repoint, transfer validation, use PID ownership, or steal
  active current-head foreign leases
- regression for PR #688 lease comment 10749 after recorded expiry

task_capability_map.py

@@ -76,6 +76,16 @@ TASK_CAPABILITY_MAP: dict[str, dict[str, str]] = {
         "permission": "gitea.pr.comment",
         "role": "reviewer",
     },
+    # #691: guarded non-owner cleanup of obsolete comment-backed reviewer leases.
+    # Apply path posts lease release + audit comments (gitea.pr.comment).
+    "cleanup_obsolete_reviewer_comment_lease": {
+        "permission": "gitea.pr.comment",
+        "role": "reviewer",
+    },
+    "gitea_cleanup_obsolete_reviewer_comment_lease": {
+        "permission": "gitea.pr.comment",
+        "role": "reviewer",
+    },
     "blind_pr_queue_review": {
         "permission": "gitea.pr.review",
         "role": "reviewer",