feat(stablediffusion-ggml): LTX-2 support + LTX-2.3 GGUF gallery entries (#9980)

stable-diffusion.cpp gained LTX-2 video generation, which requires an
audio VAE and an embeddings_connectors safetensors in addition to the
usual diffusion model, VAE, and LLM text encoder. The pinned commit
exposes audio_vae_path and embeddings_connectors_path on
sd_ctx_params_t; wire both through the option parser so gallery entries
can point at the LTX-specific assets.

Ship six LTX-2.3 GGUF gallery entries (dev + distilled, UD-Q4_K_M /
Q4_K_M / Q8_0 each) backed by a new ltx-ggml.yaml template that
defaults to euler / cfg_scale 6.0 / vae_decode_only:false /
diffusion_flash_attn / offload_params_to_cpu — matching the upstream
LTX-2 CLI recipe. Each entry pulls the model GGUF plus the QAT
gemma-3-12b-it text encoder, video VAE, audio VAE, and embeddings
connectors needed for T2V / I2V / FLF2V.


Assisted-by: Claude:claude-opus-4-7 [Claude-Code]

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>