All Runware model selections except schnell and dev were silently falling
back to runware:100@1 (FLUX.1 schnell) because COST_PER_IMAGE only had 2
entries while the image model registry (v0.13.8) expanded to 15 models.
resolve_model() falls back to schnell for any ID not in COST_PER_IMAGE,
so SD3, FLUX.2, HiDream, TwinFlow, Z-Image, Qwen-Image, Krea, and
GLM-Image all generated schnell images regardless of admin selection.
Fix: add all 15 Runware model IDs to COST_PER_IMAGE and DEFAULT_STEPS
with costs from runware.ai/pricing (April 2026). Add @see cross-ref to
the registry to prevent future drift when new models are added.