combs-formats
File-format adapter layer. The runtime and model crates never touch file
formats directly; they go through the [ModelSource] trait (the
LiteRT-LM ModelResources equivalent). Phase 1 ships the
[safetensors] adapter (HuggingFace config.json + model.safetensors,
mmap-backed, zero-copy views). GGUF / ONNX / litertlm adapters plug in
here later by implementing the same trait.