Three engines, one app — MLX and GGUF join LiteRT-LM

Edge AI Lab now runs three inference backends: LiteRT-LM, MLX, and GGUF (via llama.cpp). Each engine has an adapter behind InstrumentedEngineProtocol, so the rest of the app — conversation UI, benchmarks, eval runner, tool calling — doesn't care which backend is active. LiteRT-LM is the original. MLX brings Apple's ML framework with Metal-native compute. GGUF opens up the llama.cpp ecosystem with quantized models. Same model, three ways to run it, all on-device. The protocol-based DI means the entire test suite works against mock engines too — no real model needed for CI.