feat: merge-report lease proof fields and handoff audit (#535)

Surface lease_proof_source / recovery reason from sanctioned session
provenance on gitea_merge_pr results, and block final reports that claim
manual/seeded/injected lease proof without MCP adoption evidence.

Closes #535

merger_lease_adoption.py

@@ -7,6 +7,7 @@ after formal approval at the current PR head.
 
 from __future__ import annotations
 
+import re
 from datetime import datetime, timezone
 from typing import Any
 
@@ -133,6 +134,115 @@ def is_sanctioned_session_lease(session: dict[str, Any] | None) -> bool:
     return False
 
 
+def describe_session_lease_proof(
+    session: dict[str, Any] | None,
+) -> dict[str, Any]:
+    """Canonical merge-report lease proof fields (#535).
+
+    Surfaces how the in-session lease was established so merge handoffs can
+    distinguish sanctioned MCP acquire/adopt paths from bare manual seeding.
+    """
+    if not session:
+        return {
+            "lease_proof_source": None,
+            "lease_recovery_reason": None,
+            "lease_proof_kind": "none",
+            "lease_proof_sanctioned": False,
+            "lease_proof_comment_id": None,
+            "lease_adopted_from_session_id": None,
+        }
+
+    provenance = session.get("lease_provenance") or {}
+    if not isinstance(provenance, dict):
+        provenance = {}
+    source = (provenance.get("source") or "").strip() or None
+    sanctioned = is_sanctioned_session_lease(session)
+    reason = provenance.get("adoption_reason")
+    if isinstance(reason, str):
+        reason = reason.strip() or None
+    else:
+        reason = None
+
+    if source == SOURCE_ADOPT and sanctioned:
+        kind = "sanctioned_adoption"
+        reason = reason or DEFAULT_ADOPTION_REASON
+    elif source == SOURCE_ACQUIRE and sanctioned:
+        kind = "sanctioned_acquire"
+    elif source == SOURCE_HEARTBEAT and sanctioned:
+        kind = "sanctioned_heartbeat"
+    elif source:
+        kind = "unsanctioned"
+    else:
+        # Session present without provenance = classic manual _SESSION_LEASE seed.
+        kind = "unsanctioned_manual_seed"
+
+    comment_id = provenance.get("comment_id")
+    if comment_id is None:
+        comment_id = session.get("comment_id")
+
+    return {
+        "lease_proof_source": source,
+        "lease_recovery_reason": reason,
+        "lease_proof_kind": kind,
+        "lease_proof_sanctioned": sanctioned,
+        "lease_proof_comment_id": comment_id,
+        "lease_adopted_from_session_id": provenance.get("adopted_from_session_id"),
+    }
+
+
+# Phrases that claim non-MCP / fabricated lease proof in handoffs (#535).
+_UNSAFE_LEASE_PROOF_CLAIM_RE = re.compile(
+    r"(?is)\b("
+    r"manually\s+seeded\s+lease|"
+    r"manual(?:ly)?\s+seed(?:ed)?\s+(?:lease|proof)|"
+    r"seeded\s+lease\s+proof|"
+    r"injected\s+lease|"
+    r"lease\s+proof\s+injected|"
+    r"manual\s+_?SESSION_LEASE|"
+    r"_SESSION_LEASE\s+seed|"
+    r"unsanctioned\s+lease\s+proof"
+    r")\b"
+)
+
+# Evidence that the report used the sanctioned MCP adoption/acquire path.
+_SANCTIONED_LEASE_EVIDENCE_RE = re.compile(
+    r"(?is)\b("
+    r"gitea_adopt_merger_pr_lease|"
+    r"gitea_acquire_reviewer_pr_lease|"
+    r"lease_proof_source\s*[:=]\s*gitea_adopt_merger_pr_lease|"
+    r"lease_proof_source\s*[:=]\s*gitea_acquire_reviewer_pr_lease|"
+    r"lease_proof_kind\s*[:=]\s*sanctioned_adoption|"
+    r"lease_proof_kind\s*[:=]\s*sanctioned_acquire|"
+    r"adoption_comment_id\s*[:=]|"
+    r"sanctioned_adoption|"
+    r"mcp-review-lease-adoption"
+    r")\b"
+)
+
+
+def assess_manual_lease_proof_handoff(report_text: str) -> dict[str, Any]:
+    """Controller audit: block handoffs that claim unsafe lease seeding (#535).
+
+    Reports may discuss manual seeding as a blocked/historical anti-pattern only
+    when they also cite sanctioned MCP adoption/acquire evidence. Bare claims of
+    manual/seeded/injected lease proof without that evidence fail closed.
+    """
+    text = report_text or ""
+    if not _UNSAFE_LEASE_PROOF_CLAIM_RE.search(text):
+        return {"proven": True, "block": False, "reasons": []}
+    if _SANCTIONED_LEASE_EVIDENCE_RE.search(text):
+        return {"proven": True, "block": False, "reasons": []}
+    return {
+        "proven": False,
+        "block": True,
+        "reasons": [
+            "report claims manual/seeded/injected/unsanctioned lease proof without "
+            "sanctioned MCP adoption evidence (use gitea_adopt_merger_pr_lease / "
+            "gitea_acquire_reviewer_pr_lease and cite lease_proof_source; #535)"
+        ],
+    }
+
+
 def assess_adopt_merger_lease(
     comments: list[dict],
     *,