GET /v1/topics/:name/stream opens an SSE firehose, polled server-side
every 2s and streamed as `message` events. Forward-only — clients
hit /messages once for backfill, then live from connect-time onward.
Heartbeats every 30s keep the connection through proxies.
Web chat panel reads the stream via fetch + ReadableStream so the
bearer token stays in the Authorization header (EventSource can't
set custom headers, which would force token-in-URL leaks). Auto-
reconnect with exponential backoff. setInterval polling removed.
Vercel maxDuration bumped to 300s on the catch-all API route so
streams aren't cut at the 10s default.
drizzle migrations/meta/ deleted — superseded by the filename-
tracked custom runner in apps/broker/src/migrate.ts (c2cd67a).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>