fix(format-adapters): #270 fused-mod export correctness + comfy 0.0.04

Sharded QwenImage transformers fingerprint to arch='' so the fused-mod gate was
missed on export → bundle stored TILED mod weights without mod_gemv metadata →
reimport (fused_mod=true) decoded them as GEMV → snowflake. Fix: derive arch from
model_index.json _class_name when the fingerprint fails (alnum path-injection
guard), and widen the gate to startswith('QwenImage') so EditPlus is covered.
Pairs with the engine-side layout-authority gate (lib 0.0.09). §6.5 GO.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>