Test implementation of IJWTVerifier.

A real verifier is supplied by the application, which knows what issues its
tokens. See `wagoe.realtime.ports/IJWTVerifier`.

Redis-backed IPubSubManager: topic subscriptions in Redis sets so they are
visible cluster-wide.

Keys (optionally prefixed):
  topic:{t}  -> SET of connection-id strings
  conn:{id}  -> SET of topic strings   (reverse index)

subscribe / unsubscribe apply both SADD/SREM atomically in a MULTI/EXEC.
No explicit DEL on topic sets: Redis auto-removes a set key when its last
member is removed, so empty topics disappear and the check-then-act DEL race
cannot occur.

A server-sent events connection, registered like a WebSocket so the bus
delivers to it. `send-message` queues the message; the streaming response
body drains and renders it on its own thread, off the bus.

WebSocket connection adapter for Ring/Jetty.

Wraps Ring WebSocket implementation to provide IWebSocketConnection protocol.
Handles JSON encoding/decoding and WebSocket frame transmission.

Responsibilities (Shell/I/O):
- Send messages over WebSocket (I/O operation)
- Close WebSocket connections (I/O operation)
- JSON encoding (external format transformation)
- Error handling and logging