M11: Runner lifecycle surface (prepare/execute/finalize)

- Refactor ProcessingRunner.run() to delegate through lifecycle stages
- Add prepare(), execute(), finalize() with pass-through behavior
- Add test_runner_lifecycle_order contract test
- Preserve identical behavior; no API/CLI changes

Phase III — Runner & Service Boundary

Made-with: Cursor

modules/runtime/runner.py

@@ -1,6 +1,7 @@
 """ProcessingRunner — unified execution entrypoint for Serena pipeline.
 
 M10: Thin adapter around process_images_inner. No behavior changes.
+M11: Lifecycle surface (prepare → execute → finalize). Pass-through behavior.
 """
 
 
@@ -14,9 +15,24 @@ class ProcessingRequest:
 class ProcessingRunner:
     """
     Unified execution entrypoint for Serena processing pipeline.
+    M11: Exposes lifecycle stages for future instrumentation.
     """
 
     def run(self, request):
-        """Execute processing pipeline."""
+        """Execute processing pipeline via lifecycle stages."""
+        state = self.prepare(request)
+        result = self.execute(state)
+        return self.finalize(state, result)
+
+    def prepare(self, request):
+        """Lifecycle stage 1: prepare request. Pass-through in M11."""
+        return request
+
+    def execute(self, state):
+        """Lifecycle stage 2: run processing. Delegates to process_images_inner."""
         from modules.processing import process_images_inner
-        return process_images_inner(request.processing)
+        return process_images_inner(state.processing)
+
+    def finalize(self, state, result):
+        """Lifecycle stage 3: finalize. Pass-through in M11."""
+        return result