fix(lock): make the exact-owner renewal waiver survive downstream gates (#760)

Addresses review #499 on PR #791.

F1 — the renewal sanction was computed and then discarded twice.

`assess_issue_lock_worktree` waived base-equivalence only for
`recovery_sanctioned`, and `gitea_lock_issue` never passed the renewal waiver
into it. A branch being renewed always carries committed work, so it is never
base-equivalent, and #753 recovery refuses when the recorded PID is alive —
which is the defining condition of a renewal. Every real renewal was therefore
granted by the assessor and then rejected one gate later.

Thread `renewal_sanctioned` into `assess_issue_lock_worktree` alongside
`recovery_sanctioned`, waiving base-equivalence on the same grounds and nothing
else. Cleanliness is evaluated before the waiver and is never relaxed; the
assessment now reports which of the two waivers applied.

The MCP-level regression then exposed a second discard point: the duplicate-work
gate rejected the renewal with "open PR already covers issue" — the very PR the
lock being renewed already owns. Add `owning_pr_renewal_evidence`, the mirror of
`issue_lock_recovery.owning_pr_recovery_evidence` (#755), and carry it into the
gate only when renewal was granted. It re-checks that the PR, local, and remote
heads agree, so truncated or hand-built evidence cannot authorize an exemption.

Neither waiver is caller-supplied and `gitea_lock_issue` still gains no
parameter. Absolute wall-clock expiry is unchanged. No #790 heartbeat, sliding
expiry, fencing-token, or shared-lifecycle behavior is introduced, and #753
recovery behavior is untouched.

F2 — add tests/test_issue_760_mcp_renewal_path.py, 10 cases driving the native
`gitea_lock_issue` path against a real git repository and a real durable lock:
expired lease, live recorded PID, committed non-base-equivalent branch. Proves
the renewal completes, records prior and replacement lease evidence, advances
the generation exactly once, produces a live lock that satisfies
`verify_lock_for_mutation`, and does not claim dead-session recovery. Negative
companions prove a foreign claimant, foreign profile, unpublished branch, or
mismatched PR head cannot use the waiver, that a dirty worktree still fails
closed, and that base-equivalence still applies with no waiver at all.

Tests: new MCP suite 10 passed; combined #760 suites 50 passed; lock/lease
regression set 200 passed with 2 subtests; full suite 4240 passed, 11 failed,
6 skipped, 493 subtests passed — the same 11 pre-existing failures as the
master baseline at 3d0c13fa, no new failures.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01Ti8deB36iWcjHmE9cuxour

issue_lock_renewal.py

@@ -380,6 +380,62 @@ def assess_exact_owner_lease_renewal(
     )
 
 
+def owning_pr_renewal_evidence(
+    assessment: Mapping[str, Any] | None,
+) -> dict[str, Any] | None:
+    """Server-derived proof of the open PR a sanctioned renewal already owns.
+
+    The mirror of ``issue_lock_recovery.owning_pr_recovery_evidence`` (#755) for
+    the renewal disposition. An exact-owner renewal of a published branch is, by
+    construction, renewal of work that already has an open PR — so the
+    duplicate-work gate's linked-open-PR blocker would otherwise discard every
+    sanctioned renewal, exactly as it once discarded every sanctioned recovery.
+
+    Returns ``None`` unless renewal was actually granted and the evidence names
+    one owning PR whose head agrees with both the local and remote heads the
+    assessor accepted. Nothing is caller-supplied: every field is copied from
+    evidence built out of durable lock state plus live git/Gitea observation.
+
+    Renewal has no descendant case — it requires the local, remote, and PR heads
+    to be equal — so there is only one head to report.
+    """
+    if not isinstance(assessment, Mapping):
+        return None
+    if assessment.get("outcome") != RENEWAL_SANCTIONED:
+        return None
+    if not assessment.get("renewal_sanctioned"):
+        return None
+
+    evidence = assessment.get("evidence") or {}
+    branch_name = _text(evidence.get("branch_name"))
+    pr_head = _text(evidence.get("pr_head_sha"))
+    local_head = _text(evidence.get("head_sha"))
+    remote_head = _text(evidence.get("remote_head_sha"))
+    raw_pr_number = evidence.get("pr_number")
+
+    if raw_pr_number is None or not branch_name or not pr_head:
+        return None
+    # The assessor already required these to agree. Re-check, so a truncated or
+    # hand-built evidence map can never authorize an exemption.
+    if pr_head != local_head or pr_head != remote_head:
+        return None
+    try:
+        pr_number = int(raw_pr_number)
+        issue_number = int(evidence.get("issue_number"))
+    except (TypeError, ValueError):
+        return None
+
+    return {
+        "issue_number": issue_number,
+        "pr_number": pr_number,
+        "branch_name": branch_name,
+        "head_sha": pr_head,
+        "recorded_head": pr_head,
+        "accepted_head": pr_head,
+        "head_relation": "equal",
+    }
+
+
 def build_renewal_record(
     assessment: Mapping[str, Any] | None,
     *,