Add test_integration_e2e.py that exercises the full loader → generator
→ composer pipeline with GreyBackend, asserting 2 pages, 4 panels, and
cache-hit behaviour on second run (PNG round-trip tolerance atol=1/255).
Add examples/workflows/m1_basic_vertical_stack.json as a reference
ComfyUI workflow JSON wiring CheckpointLoaderSimple → ComicScriptLoader
→ ComicBatchGenerator → ComicPageComposer → SaveImage.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>