Subscribe to durable market and account events over SSE.

Server-Sent Events stream. Pass comma-separated topics; schemaVersion defaults to 2. Legacy schemaVersion=1 remains available for exactly one topic per connection. Version 2 event ids are stable source identities while SSE id: is an opaque source-vector resume cursor. Public streams include market books, trades and lifecycle updates. Verified sessions can subscribe only to their own user streams. Replay is served from the durable Postgres journals; a reset frame explicitly signals retention, generation or restoration discontinuities.