Create (or revive) a relay tunnel for a named project server

Registers a server record named name if missing, mints a relay tunnel grant for it, and persists the tunnel bearer URL (including the plaintext ?k= secret) onto the server record's url so evals and chatboxes can target the tunnel like any remote server. The plaintext persistence is a deliberate trade-off of the current tunnel MVP — the backend otherwise stores only a hash of the secret — mitigated by rotation: every call rotates the secret, revokes the previous grant at the edge (disconnecting any live tunnel session for the server), and updates the stored URL, so re-calling this route is also the rotation/recovery path.

The caller hosts the tunnel itself: connect a WebSocket to relayWsUrl (subprotocol mcpjam-tunnel.v1, Authorization: Bearer <connectToken>) and serve the relayed requests — this is what mcpjam tunnel does. When the host disconnects, the server record stays and calls to the public URL fail fast at the edge.