Realtime stream (WebSocket)

Upgrade to a WebSocket. Authenticate with ?api_key= (browsers cannot set headers).

Client → server: {"type":"subscribe","topics":["all"]}, {"type":"unsubscribe","topics":[…]}, {"type":"ping"}.

Server → client: hello, subscribed, unsubscribed, pong, heartbeat (every 25 s), error, and events

(update.created with data = FeedItem, program.changed, notification).

Topics: all, frontier:<slug>, company:<slug>, program:<company>/<program>, user:<id> (dev: requires matching x-user-email/user_email).