audio.cpp adds music and SFX generation to GGML native framework

The audio.cpp library now supports ACE-Step 1.5, Stable Audio 3, and HeartMuLa via GGML, enabling music and SFX generation alongside speech processing. HeartMuLa can generate 10-minute audio segments, with ACE-Step Turbo achieving a 9.97x real-time factor in C++ compared to slower Python implementations.