fix: close ungated CLI merge bypasses in review_pr.py and merge_pr.py (#16)

Reviewer found the MCP merge surface is gated but two local CLI scripts remain
ungated merge paths that LLM automations in this project have been using.
Close them (Option B — minimal safe fix; full gated CLI merge left to a
follow-up):

- review_pr.py: `--merge` now fails closed BEFORE any API call with a clear
  message directing callers to the gated `gitea_merge_pr` MCP workflow. The
  review-only path is unchanged. The merge execution block was removed.
- merge_pr.py: main() is now a fail-closed no-op — reads no credentials and
  makes no merge API call; prints that merge is only available via the gated
  workflow.
- README: the `review_pr.py` row and Quick Examples no longer advertise a CLI
  `--merge` path; added an audit-logging clarification that #16 returns
  structured gate/merge results but does not add durable audit logging, which
  is tracked by #18.

Tests updated/added:
- test_review_pr.py: `--merge` fails closed with no API call; message points to
  the gated workflow.
- test_merge_pr.py: merge fails closed with no API call, even with
  --force/--do/--title/--message; message points to the gated workflow.
- test_mcp_server.py: README no longer advertises the ungated CLI merge example.

The gated MCP `gitea_merge_pr` is unchanged and still gated; `gitea_review_pr`
still fails closed on merge=True; `gitea_submit_pr_review` still cannot merge.
No secrets, auth headers, raw env, or credential paths are exposed. No
Jenkins/Ops/GlitchTip/Release/deploy/CI behavior added. #17/#18 not started.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_review_pr.py

@@ -65,27 +65,34 @@ class TestAPIPayload(unittest.TestCase):
 
     @patch("review_pr.api_request")
     @patch("review_pr.get_auth_header", return_value=FAKE_CREDS)
-    def test_approve_and_merge_workflow(self, _auth, mock_api):
-        # Setup mock api_request to return PR details, review response, and merge response
-        mock_api.side_effect = [FAKE_PR_DATA, {}, {}]
-
+    def test_merge_flag_fails_closed_without_api_call(self, _auth, mock_api):
+        # --merge is an ungated bypass and is disabled (#16). It must fail
+        # closed BEFORE any API call — no review, no merge.
         rc = review_pr.main([
             "--pr-number", "81",
             "--event", "APPROVE",
             "--body", "Approved",
             "--merge",
-            "--merge-method", "squash"
+            "--merge-method", "squash",
         ])
-        self.assertEqual(rc, 0)
-        self.assertEqual(mock_api.call_count, 3)
+        self.assertEqual(rc, 2)
+        self.assertEqual(mock_api.call_count, 0)
 
-        # Verify third call: POST merge
-        third_call_args = mock_api.call_args_list[2]
-        self.assertEqual(third_call_args[0][0], "POST")
-        self.assertEqual(third_call_args[0][1], "https://gitea.dadeschools.net/api/v1/repos/Contractor/Timesheet/pulls/81/merge")
-        payload = third_call_args[0][3]
-        self.assertEqual(payload["Do"], "squash")
-        self.assertEqual(payload["force_merge"], False)
+    def test_merge_flag_message_points_to_gated_workflow(self):
+        import io
+        import contextlib
+        with patch("review_pr.get_auth_header", return_value=FAKE_CREDS), \
+                patch("review_pr.api_request") as mock_api:
+            buf = io.StringIO()
+            with contextlib.redirect_stderr(buf):
+                rc = review_pr.main([
+                    "--pr-number", "81", "--event", "APPROVE", "--merge",
+                ])
+        self.assertEqual(rc, 2)
+        self.assertEqual(mock_api.call_count, 0)
+        msg = buf.getvalue().lower()
+        self.assertIn("disabled", msg)
+        self.assertIn("gitea_merge_pr", msg)
 
 
 if __name__ == "__main__":