feat(demo): add pipeline visualization demo mode

- Add --pipeline-demo flag for ASCII pipeline animation
- Create engine/pipeline_viz.py with animated pipeline graphics
- Shows data flow, camera modes, FPS counter
- Run with: python mainline.py --pipeline-demo --display pygame

engine/config.py

@@ -244,6 +244,7 @@ WEBSOCKET_PORT = _arg_int("--websocket-port", 8765)
 # ─── DEMO MODE ────────────────────────────────────────────
 DEMO = "--demo" in sys.argv
 DEMO_EFFECT_DURATION = 5.0  # seconds per effect
+PIPELINE_DEMO = "--pipeline-demo" in sys.argv
 
 # ─── PIPELINE DIAGRAM ────────────────────────────────────
 PIPELINE_DIAGRAM = "--pipeline-diagram" in sys.argv