Provider-agnostic session layer for the base project: a shared client/server
wire protocol, a RealtimeProvider adapter interface, and an OpenAI Realtime
implementation of it, wired through a WebSocket relay (browser <-> our
SvelteKit server <-> OpenAI) so the API key never reaches the browser and
future providers/pipelines can be added without touching client code.
Switches the adapter to adapter-node and adds a custom server.js + dev-mode
Vite plugin, since SvelteKit has no native WebSocket support yet.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>