feat(guard): harden workflow against unattributed root WIP and pytest-disabled production guards (Closes #683)

Add shared workflow_scope_guard with typed blockers (blocker_kind +
exact_next_action) and force-on production enforcement under pytest.
Wire root/branches/scope checks through verify_preflight_purity and
mutation entrypoints (create_issue, comment_issue) without adopting the
rejected 300a4ca patterns (test-mode early-return, porcelain *.py filter).

Regression suite covers out-of-scope issue ownership, root diagnostic
edits, worktree bind success path, force-on under pytest, porcelain
integrity, monkeypatch resistance, real entrypoint fail-closed proof,
and durable failure recording.

tests/test_issue_540_comment_role_poison.py

@@ -267,10 +267,19 @@ class TestReconcilerCommentThroughCanonicalPath(unittest.TestCase):
             with patch.dict(os.environ, {}, clear=False):
                 os.environ.pop("GITEA_AUTHOR_WORKTREE", None)
                 os.environ.pop("GITEA_ACTIVE_WORKTREE", None)
-                with self.assertRaises(RuntimeError):
-                    srv.gitea_create_issue_comment(
+                try:
+                    res = srv.gitea_create_issue_comment(
                         515, "author note", remote="prgs"
                     )
+                except RuntimeError:
+                    pass  # legacy raise path
+                else:
+                    # #683: typed blocker at mutation entrypoint
+                    self.assertFalse(res.get("success"))
+                    self.assertFalse(res.get("performed"))
+                    self.assertTrue(
+                        res.get("blocker_kind") or res.get("reasons")
+                    )
         mock_api.assert_not_called()