feat: add skip-stale-REQUEST_CHANGES reviewer menu prompt (#482)

Add a second reviewer workflow prompt to the root MCP operator menu:
"Skip already-reviewed stale REQUEST_CHANGES PR and hand off to author".

show_reviewer_prompts becomes a small 2-option submenu (mirroring the
existing show_author_prompts idiom): option 1 keeps the standard PR
review prompt; option 2 is the new prompt. It instructs the reviewer to
determine whether the current head already carries a non-stale
REQUEST_CHANGES verdict and, if so, to submit no new terminal review
mutation, run only handoff diagnostics, and return an author-ready fix
prompt with the full 8-field handoff.

Stacked on PR #479 (feat/issue-478-mcp-menu-shell); the menu is not yet
on master. Diff limited to the new prompt: mcp-menu.sh, docs/mcp-menu.md,
and a discoverability test in tests/test_mcp_menu_script.py.

Closes #482.

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

tests/test_mcp_menu_script.py

@@ -105,6 +105,19 @@ class TestMcpMenuScript(unittest.TestCase):
         self.assertIn("./mcp-menu.sh", docs_text)
         self.assertIn("placeholder", docs_text.lower())
 
+    def test_reviewer_skip_stale_request_changes_prompt_discoverable(self):
+        # #482: the skip-already-reviewed-stale-REQUEST_CHANGES reviewer prompt
+        # must be reachable from the reviewer menu and documented.
+        label = "Skip already-reviewed stale REQUEST_CHANGES PR and hand off to author"
+        reviewer_fn = self._extract_function("show_reviewer_prompts")
+        self.assertIn(label, reviewer_fn, "new reviewer prompt label must appear in the reviewer menu")
+        # The prompt must instruct: no duplicate terminal review mutation for a
+        # non-stale REQUEST_CHANGES head, and must carry the author handoff.
+        self.assertIn("do NOT submit another terminal review mutation", reviewer_fn)
+        self.assertIn("author-ready fix prompt", reviewer_fn)
+        docs_text = DOCS.read_text(encoding="utf-8")
+        self.assertIn("REQUEST_CHANGES", docs_text)
+
     def _extract_function(self, name: str) -> str:
         marker = f"{name}() {{"
         start = self.content.index(marker)