Durable Actors 0.7.7

WebSocket grants now return a signed gateway URL without waiting for actor activation. The gateway resolves the actor when the client connects and preserves the original authorization deadline.

Socket authorization and authorized socket effects check persisted ownership without fetching actor snapshots. Actor, host, session, epoch, and lease checks remain enforced.

No client application changes are required. Cold actor startup still occurs before the WebSocket handshake completes.

Changes: #139