fix: resolve test suite regressions and conn helper discovery error

tests/test_author_mutation_worktree.py

@@ -81,13 +81,14 @@ class TestPreflightIntegration(unittest.TestCase):
         mcp_server._preflight_resolved_role = "author"
         control_root = "/repo/Gitea-Tools"
         with mock.patch.object(mcp_server, "PROJECT_ROOT", control_root):
-            with mock.patch.dict(
-                "os.environ",
-                {"GITEA_TEST_PORCELAIN": ""},
-                clear=False,
-            ):
-                with self.assertRaises(RuntimeError) as ctx:
-                    mcp_server.verify_preflight_purity()
+            with mock.patch.object(mcp_server, "_enforce_root_checkout_guard"):
+                with mock.patch.dict(
+                    "os.environ",
+                    {"GITEA_TEST_PORCELAIN": ""},
+                    clear=False,
+                ):
+                    with self.assertRaises(RuntimeError) as ctx:
+                        mcp_server.verify_preflight_purity()
         self.assertIn("Branches-only mutation guard", str(ctx.exception))
 
     def test_verify_preflight_allows_branches_worktree(self):
@@ -97,12 +98,13 @@ class TestPreflightIntegration(unittest.TestCase):
         mcp_server._preflight_capability_called = True
         mcp_server._preflight_resolved_role = "author"
         worktree = "/repo/Gitea-Tools/branches/issue-274"
-        with mock.patch.dict(
-            "os.environ",
-            {"GITEA_TEST_PORCELAIN": ""},
-            clear=False,
-        ):
-            mcp_server.verify_preflight_purity(worktree_path=worktree)
+        with mock.patch.object(mcp_server, "_enforce_root_checkout_guard"):
+            with mock.patch.dict(
+                "os.environ",
+                {"GITEA_TEST_PORCELAIN": ""},
+                clear=False,
+            ):
+                mcp_server.verify_preflight_purity(worktree_path=worktree)
 
 
 if __name__ == "__main__":