UPSTREAM PR #18641: [Do Not Merge] model : LFM2.5-Audio-1.5B

[loci-dev]

Mirrored from ggml-org/llama.cpp#18641

Liquid AI released LFM2.5-Audio-1.5B.

LFM2.5-Audio-1.5B is Liquid AI's updated end-to-end audio foundation model. Key improvements include a custom, LFM based audio detokenizer, llama.cpp compatible GGUFs for CPU inference, and better ASR and TTS performance.

This PR is intended to provide a functional implementation in llama.cpp until necessary infrastructure is implemented.
The plan is to partially merge it into upstream, while keeping and tracking functional implementation here. It will be rebased from time to time.

GGUFs, precompiled runners, and instructions, live in https://huggingface.co/LiquidAI/LFM2.5-Audio-1.5B-GGUF.

Merge plan:

• Support n_embd_out, done in model : add LFM2-ColBert-350M ggml-org/llama.cpp#18607
• Support llama_memory_hybrid_iswa
• istft for audio output
• tbd

Demo of capabilities

demo.mp4

Thank you, @ngxson for the help!