### Changed
- Raised the Runtime floor to `AbstractRuntime[multimodal,mcp-worker]>=0.4.20` across the base, Apple, and GPU install profiles.
- Gateway's legacy prompt-cache snapshot aliases, `GET /api/gateway/prompt_cache/saved` and `POST /api/gateway/prompt_cache/save|load`, now delegate to Runtime's public host facade instead of using provider-private prompt-cache state directly.
- Local bundle runtimes now keep host-local prompt-cache exports under `<DATA_DIR>/prompt_cache_exports` through Runtime's export root policy.

### Fixed
- Removed the last Gateway-side prompt-cache boundary bypass (`runtime._abstractcore_llm_client`, direct provider-instance access, and provider-private `_prompt_cache_store` / GGUF cache hooks) from the public route surface.
- Removed the stale internal Core catalog proxy module after discovery routing fully moved to Runtime's public discovery facade.
