M10: ProcessingRunner skeleton

- Add modules/runtime/runner.py with ProcessingRunner and ProcessingRequest
- Wire process_images to delegate through runner (internal only)
- Add test/quality/test_processing_runner.py contract test

Behavior-preserving. Zero blast radius. All callers unchanged.

Made-with: Cursor

modules/runtime/__init__.py

@@ -0,0 +1,4 @@
+"""Runtime execution boundary for Serena.
+
+M10: ProcessingRunner skeleton. Thin adapter around process_images_inner.
+"""

modules/runtime/runner.py

@@ -0,0 +1,22 @@
+"""ProcessingRunner — unified execution entrypoint for Serena pipeline.
+
+M10: Thin adapter around process_images_inner. No behavior changes.
+"""
+
+
+class ProcessingRequest:
+    """Wraps StableDiffusionProcessing for runner boundary."""
+
+    def __init__(self, processing):
+        self.processing = processing
+
+
+class ProcessingRunner:
+    """
+    Unified execution entrypoint for Serena processing pipeline.
+    """
+
+    def run(self, request):
+        """Execute processing pipeline."""
+        from modules.processing import process_images_inner
+        return process_images_inner(request.processing)