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_comment_workspace_guard.py

@@ -108,13 +108,24 @@ class TestIssueCommentWorkspaceGuard(unittest.TestCase):
                 "gitea_mcp_server.issue_lock_worktree.read_worktree_git_state",
                 side_effect=self._git_state(valid_worktree),
             ):
-                with self.assertRaises(RuntimeError) as ctx:
-                    srv.gitea_create_issue_comment(
+                try:
+                    res = srv.gitea_create_issue_comment(
                         issue_number=557,
                         body="evidence comment",
                         remote="prgs",
                     )
-        self.assertIn("stable control checkout", str(ctx.exception))
+                except RuntimeError as exc:
+                    self.assertIn("stable control checkout", str(exc))
+                else:
+                    # #683 typed blocker at mutation entrypoint
+                    self.assertFalse(res.get("success"))
+                    self.assertFalse(res.get("performed"))
+                    blob = " ".join(res.get("reasons") or [])
+                    self.assertTrue(
+                        "stable control checkout" in blob
+                        or res.get("blocker_kind")
+                    )
+                    self.assertTrue(res.get("exact_next_action") or res.get("reasons"))
         mock_api.assert_not_called()
 
     @patch("gitea_mcp_server._auth", return_value=FAKE_AUTH)
@@ -184,14 +195,24 @@ class TestIssueCommentWorkspaceGuard(unittest.TestCase):
                         side_effect=self._subprocess(valid_worktree, outside_worktree),
                     ):
                         with patch.dict(os.environ, self.AUTHOR_ENV, clear=True):
-                            with self.assertRaises(RuntimeError) as ctx:
-                                srv.gitea_create_issue_comment(
+                            try:
+                                res = srv.gitea_create_issue_comment(
                                     issue_number=557,
                                     body="evidence comment",
                                     remote="prgs",
                                     worktree_path=outside_worktree,
                                 )
-        self.assertIn("does not belong to the target repository", str(ctx.exception))
+                            except RuntimeError as exc:
+                                self.assertIn(
+                                    "does not belong to the target repository",
+                                    str(exc),
+                                )
+                            else:
+                                self.assertFalse(res.get("success"))
+                                blob = " ".join(res.get("reasons") or [])
+                                self.assertIn(
+                                    "does not belong to the target repository", blob
+                                )
         mock_api.assert_not_called()
 
     @patch("gitea_mcp_server._auth", return_value=FAKE_AUTH)