feat(pipeline): add self-documenting pipeline introspection

- Add --pipeline-diagram flag to generate mermaid diagrams
- Create engine/pipeline.py with PipelineIntrospector
- Outputs flowchart, sequence diagram, and camera state diagram
- Run with: python mainline.py --pipeline-diagram

engine/app.py

@@ -559,6 +559,13 @@ def run_demo_mode():
 
 
 def main():
+    from engine import config
+    from engine.pipeline import generate_pipeline_diagram
+
+    if config.PIPELINE_DIAGRAM:
+        print(generate_pipeline_diagram())
+        return
+
     if config.DEMO:
         run_demo_mode()
         return