fix(app_controller): restore context_to_send definition in _api_generate (CRITICAL regression from ai_loop_regressions_20260614)

src/app_controller.py

@@ -275,6 +275,10 @@ def _api_generate(controller: 'AppController', req: GenerateRequest) -> dict[str
       "ts": project_manager.now_ts()
       })
       
+   with controller._disc_entries_lock:
+    has_ai_response = any(e.get("role") == "AI" for e in controller.disc_entries)
+   context_to_send = stable_md if not has_ai_response else ""
+
    result = ai_client.send_result(context_to_send, user_msg, base_dir, controller.last_file_items, disc_text, rag_engine=None)
    if not result.ok:
     err = result.errors[0]