Extend the per-LoRA key_filter (LoRA Stack + Stack Dynamic) with audio_only and
no_audio, so audio-video models (LTX-2, ACE-Step) can route audio vs video layers
per LoRA without a new field. A layer is 'audio' when 'audio' appears in its LoRA
prefix or resolved model key (audio_embeddings_connector, audio_adaln_single,
audio_patchify_proj, audio_proj_out, av_ca_audio_*, per-block audio sublayers).
Applied at the same two filter sites as shared_only/unique_only. Use cases: merge
two LTX LoRAs keeping one's sound (others -> no_audio); audio LoRA + video LoRA
(audio_only + no_audio). Tests + README/wiki updated; 275 passing.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
