feat: comment-then-stop policy for partial PR reconciliation (Closes #302)

Already-landed PR reconciliation could prove a PR should be closed but
stop silently when gitea.pr.close was unavailable, even with comment
capability present. Adopt Option B (comment-then-stop) as the durable
policy and enforce it:

- resolve_partial_reconciliation_plan maps proven capabilities to one
  of four outcomes: FULL_RECONCILE_CLOSE_ALLOWED (close_pr proven),
  PARTIAL_RECONCILE_COMMENT_THEN_STOP (comment_pr proven, close_pr
  missing; one reconciliation comment with PR head SHA, target branch
  SHA, ancestor proof, linked issue status, and the missing capability,
  then stop), RECOVERY_HANDOFF_ONLY (no comment capability; no Gitea
  mutation), and GATE_NOT_PROVEN (no ancestry proof; no mutation
  regardless of capability). Missing capability dicts fail closed.
- assess_partial_reconciliation_report requires final reports to
  explain why the comment was or was not posted, name the missing
  capability, and state the close result or that no mutation ran.
- workflows/reconcile-landed-pr.md gains section 12A documenting the
  policy; the workflow contract test locks the new markers.

Tests cover close capability present, close missing with comment
allowed, comment capability missing, all capabilities missing,
unproven ancestry, fail-closed capability dict, and report checks for
each outcome.

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

tests/test_review_proofs.py

@@ -24,6 +24,8 @@ from review_proofs import (  # noqa: E402
     ISSUE_SELECTION_CONTINUATION_EXPLICIT,
     ISSUE_SELECTION_REPRESENTED_BY_OPEN_PR,
     assess_author_pr_report,
+    assess_partial_reconciliation_report,
+    resolve_partial_reconciliation_plan,
     assess_queue_ordering_proof,
     assess_reviewer_baseline_validation_proof,
     assess_capability_evidence,
@@ -2539,5 +2541,132 @@ class TestReviewerBaselineValidationProof(unittest.TestCase):
         self.assertFalse(report["baseline_validation_proven"])
 
 
+class TestPartialReconciliationPlan(unittest.TestCase):
+    """Issue #302: policy when PR-close capability is missing (Option B)."""
+
+    def _plan(self, **overrides):
+        kwargs = {
+            "ancestor_proven": True,
+            "capabilities": {
+                "close_pr": False,
+                "comment_pr": True,
+                "close_issue": True,
+                "comment_issue": True,
+            },
+        }
+        kwargs.update(overrides)
+        return resolve_partial_reconciliation_plan(**kwargs)
+
+    def test_close_capability_present_allows_full_reconcile(self):
+        plan = self._plan(capabilities={
+            "close_pr": True, "comment_pr": True,
+            "close_issue": True, "comment_issue": True,
+        })
+        self.assertEqual(plan["outcome"], "FULL_RECONCILE_CLOSE_ALLOWED")
+        self.assertIn("close_pr", plan["allowed_mutations"])
+
+    def test_close_missing_with_comment_posts_comment_then_stops(self):
+        plan = self._plan()
+        self.assertEqual(
+            plan["outcome"], "PARTIAL_RECONCILE_COMMENT_THEN_STOP")
+        self.assertEqual(plan["allowed_mutations"], ("comment_pr",))
+        for field in (
+            "PR head SHA",
+            "target branch SHA",
+            "ancestor proof",
+            "linked issue status",
+            "required missing capability",
+        ):
+            self.assertIn(field, plan["required_comment_fields"])
+
+    def test_comment_capability_missing_produces_handoff_only(self):
+        plan = self._plan(capabilities={
+            "close_pr": False, "comment_pr": False,
+            "close_issue": True, "comment_issue": True,
+        })
+        self.assertEqual(plan["outcome"], "RECOVERY_HANDOFF_ONLY")
+        self.assertEqual(plan["allowed_mutations"], ())
+
+    def test_all_capabilities_missing_produces_handoff_only(self):
+        plan = self._plan(capabilities={
+            "close_pr": False, "comment_pr": False,
+            "close_issue": False, "comment_issue": False,
+        })
+        self.assertEqual(plan["outcome"], "RECOVERY_HANDOFF_ONLY")
+        self.assertEqual(plan["allowed_mutations"], ())
+
+    def test_unproven_ancestry_blocks_all_mutations(self):
+        plan = self._plan(ancestor_proven=False, capabilities={
+            "close_pr": True, "comment_pr": True,
+            "close_issue": True, "comment_issue": True,
+        })
+        self.assertEqual(plan["outcome"], "GATE_NOT_PROVEN")
+        self.assertEqual(plan["allowed_mutations"], ())
+
+    def test_missing_capability_dict_fails_closed(self):
+        plan = self._plan(capabilities=None)
+        self.assertEqual(plan["outcome"], "RECOVERY_HANDOFF_ONLY")
+        self.assertEqual(plan["allowed_mutations"], ())
+
+
+class TestPartialReconciliationReport(unittest.TestCase):
+    """Issue #302: reports must explain why comments were or were not posted."""
+
+    def _plan(self, outcome):
+        capabilities = {
+            "FULL_RECONCILE_CLOSE_ALLOWED": {
+                "close_pr": True, "comment_pr": True,
+                "close_issue": True, "comment_issue": True,
+            },
+            "PARTIAL_RECONCILE_COMMENT_THEN_STOP": {
+                "close_pr": False, "comment_pr": True,
+                "close_issue": True, "comment_issue": True,
+            },
+            "RECOVERY_HANDOFF_ONLY": {
+                "close_pr": False, "comment_pr": False,
+                "close_issue": False, "comment_issue": False,
+            },
+        }[outcome]
+        return resolve_partial_reconciliation_plan(
+            ancestor_proven=True, capabilities=capabilities)
+
+    def test_partial_report_requires_comment_and_missing_capability(self):
+        plan = self._plan("PARTIAL_RECONCILE_COMMENT_THEN_STOP")
+        good = (
+            "Reconciliation comment posted on PR #278 with ancestor proof. "
+            "PR close skipped: close capability gitea.pr.close missing; "
+            "stopped for authorized close."
+        )
+        result = assess_partial_reconciliation_report(good, plan=plan)
+        self.assertTrue(result["complete"])
+
+        bad = "Stopped. Nothing done."
+        result = assess_partial_reconciliation_report(bad, plan=plan)
+        self.assertTrue(result["block"])
+
+    def test_handoff_only_report_requires_no_comment_explanation(self):
+        plan = self._plan("RECOVERY_HANDOFF_ONLY")
+        good = (
+            "No reconciliation comment posted: comment capability missing. "
+            "No Gitea mutation performed; recovery handoff produced."
+        )
+        result = assess_partial_reconciliation_report(good, plan=plan)
+        self.assertTrue(result["complete"])
+
+        bad = "Recovery handoff produced."
+        result = assess_partial_reconciliation_report(bad, plan=plan)
+        self.assertTrue(result["block"])
+
+    def test_full_reconcile_report_requires_close_result(self):
+        plan = self._plan("FULL_RECONCILE_CLOSE_ALLOWED")
+        good = "PR close result: closed PR #278 after ancestor proof."
+        result = assess_partial_reconciliation_report(good, plan=plan)
+        self.assertTrue(result["complete"])
+
+        bad = "Reconciliation done."
+        result = assess_partial_reconciliation_report(bad, plan=plan)
+        self.assertTrue(result["block"])
+
+
 if __name__ == "__main__":
     unittest.main()