V4: integrate SeedAnce systems into production pipeline + storyboard

Phase 4 of SeedAnce 2.0 approximation — integration:
- produce_trailer_v4.py: wire IdentityKeeper, RewardEnsemble, AccelerationManager
  into chained shot generation with per-shot quality scoring + identity verification
- fanren_trailer_v4.json: add acceleration_preset, quality_threshold,
  identity_enforcement fields
- .gitignore: track produce_trailer_v4.py

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: charliewwdev

.gitignore

@@ -20,6 +20,7 @@ scripts/*
 !scripts/story.py
 !scripts/produce_trailer_v2.py
 !scripts/produce_trailer_v3.py
+!scripts/produce_trailer_v4.py
 !scripts/__init__.py
 
 *.ipynb

examples/fanren_trailer_v4.json

@@ -40,6 +40,10 @@
     "cross_shot_harmonize": true
   },
 
+  "acceleration_preset": "balanced",
+  "quality_threshold": 0.65,
+  "identity_enforcement": "reference",
+
   "postprocess": {
     "upscale": {"model": "animevideov3", "scale": 2},
     "interpolation": {"multiplier": 2, "backend": "auto"},