[mcp] Add dummy tools for previously called but currently missing tools. (#17853)

- [x] Add dummy tools for previously called but currently missing tools.
Currently supporting MCP tools only.

codex-rs/features/src/tests.rs

@@ -133,6 +133,15 @@ fn tool_search_is_under_development_and_disabled_by_default() {
     assert_eq!(Feature::ToolSearch.default_enabled(), false);
 }
 
+#[test]
+fn unavailable_dummy_tools_is_under_development_and_disabled_by_default() {
+    assert_eq!(
+        Feature::UnavailableDummyTools.stage(),
+        Stage::UnderDevelopment
+    );
+    assert_eq!(Feature::UnavailableDummyTools.default_enabled(), false);
+}
+
 #[test]
 fn general_analytics_is_stable_and_enabled_by_default() {
     assert_eq!(Feature::GeneralAnalytics.stage(), Stage::Stable);