Add /api/chat: mesh-hydrated chat with multi-provider failover (groq·gemini·opencode_zen·huggingface·xai) + live-API docs

rebrand: ToolTuner → SignalMesh everywhere — name, titles, user-agents, default values, README tags

Add HuggingFace Space deployment: ToolTuner REST API with all 3 tools

Initial Release: Signal Mesh Spatially Indexed Orchestrator