Newsence Core Worker

HTTP endpoints (frontend):
GET  /health
*    /preview                    - Scrape-only
POST /submit                     - Submit URL
POST /embed                      - Generate embeddings
GET  /status/:instanceId         - Workflow status (JSON)
GET  /stream/:instanceId         - Workflow status (SSE)

Bot endpoints are exposed as RPC methods on the CoreWorker class —
reachable only through the service binding from `newsence-bot`.