feat: block issue closure on unproven expected pre-existing failure (#529)

Delivers #529 acceptance criterion 6: controller issue closure must be
blocked when the closure report calls a non-zero test-suite exit an
"expected pre-existing"/baseline failure without pre-merge proof.

- controller_closure_baseline_proof.py: assess_controller_closure_baseline_proof
  reuses the #533 pre-merge baseline verifier; empty report -> skipped/allowed,
  clean pass -> allowed, proven baseline -> allowed, unproven baseline -> block.
- gitea_close_issue: optional closure_report param; fails closed (no state PATCH)
  when the gate blocks.
- final_report_validator: new controller_close task kind (alias close_issue)
  wired to the pre-merge baseline proof rule so a closure can be pre-checked.
- Tests: tests/test_controller_closure_baseline_proof.py plus two
  gitea_close_issue gate tests.

Scope: criteria 2/3 (non-zero exit not a clean pass; baseline claims need
proof) are already enforced on master via premerge_baseline_proof (#533) and
the reviewer schema rules. Criteria 1/4/5 (post-merge moot canonical wording
and validation:* process-state labels) remain follow-up work.

Validation: full suite 2365 passed, 6 skipped; the 9 remaining failures
(tests/test_config.py TestAuthIntegration, tests/test_credentials.py
TestGetCredentials, test_issue_540 reviewer-role) are baseline-proven —
identical failures on clean prgs/master 6913ac9 (keychain/env dependent),
unrelated to this change.

Refs #529

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

final_report_validator.py

@@ -40,6 +40,7 @@ FINAL_REPORT_TASK_KINDS = frozenset({
     "issue_filing",
     "issue_selection",
     "inventory",
+    "controller_close",
 })
 
 _TASK_KIND_ALIASES = {
@@ -51,6 +52,9 @@ _TASK_KIND_ALIASES = {
     "reconcile_already_landed": "reconcile_already_landed",
     "work-issue": "work_issue",
     "create_issue": "issue_filing",
+    "close_issue": "controller_close",
+    "close-issue": "controller_close",
+    "controller-close": "controller_close",
 }
 
 _HANDOFF_ROLE_BY_TASK = {
@@ -62,6 +66,7 @@ _HANDOFF_ROLE_BY_TASK = {
     "issue_filing": "issue_filing",
     "issue_selection": None,
     "inventory": "inventory",
+    "controller_close": None,
 }
 
 _LEGACY_WORKSPACE_MUTATIONS_RE = re.compile(
@@ -1606,6 +1611,13 @@ _RULES_BY_TASK: dict[str, list[Callable[..., list[dict[str, str]]]]] = {
         *_SHARED_CANONICAL_COMMENT_RULES,
         *_SHARED_ISSUE_LOCK_RULES,
     ],
+    # Controller issue closure (#529): a closure report must not bury an
+    # unproven non-zero suite exit as an "expected pre-existing failure".
+    # Kept intentionally narrow so a closure pre-check does not demand the
+    # full reviewer/author handoff schema.
+    "controller_close": [
+        _rule_reviewer_premerge_baseline_proof,
+    ],
 }