JWT verification adapter that delegates to boundary/user module.

Wraps boundary.user.shell.auth/validate-jwt-token to provide IJWTVerifier
protocol implementation. Avoids direct dependency from core layer to user module.

Responsibilities (Shell/I/O):
- Call user module for JWT verification (I/O - external dependency)
- Transform user module response to expected format
- Handle verification errors

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

In-memory connection registry implementation.

Stores active WebSocket connections in an atom for single-server deployments.
For multi-server scaling, swap with Redis-backed registry implementation.

Registry Structure:
  {connection-id {:connection <Connection record>
                  :ws-adapter <IWebSocketConnection>}}

Responsibilities (Shell/I/O):
- Store and retrieve connection mappings (stateful atom)
- Filter connections by user-id, role (uses core filtering functions)
- Thread-safe updates (atom swap operations)

In-memory pub/sub topic management (imperative shell).

Implements IPubSubManager protocol using atom-based subscription storage.
Coordinates between pure pub/sub core functions and stateful subscription
management.

Single-server implementation - subscriptions stored in memory. For
multi-server deployments, would need Redis-backed implementation (v0.2.0).

Thread-safe via atom swap operations.

Realtime service implementation (Shell layer).

Orchestrates WebSocket messaging between core logic and adapters.
Implements the imperative shell in the FC/IS architecture pattern.

Responsibilities (Shell/I/O):
- WebSocket connection lifecycle (open, close)
- JWT authentication (delegates to user module)
- Message routing (uses core routing logic)
- Connection registry management
- Pub/sub topic management
- Logging and error handling

Does NOT contain:
- Business logic (lives in core.*)
- Database operations (no persistence needed for WebSockets)
- Message validation logic (lives in core.message)