reconnect() holds the pool slot while sleeping between attempts #10

Session::reconnect() sleeps retry_interval between passes and walks all endpoints while still holding its pool slot. With defaults (3 endpoints, 3 attempts, 1s interval) the worst case is ~92s, during which concurrent acquire() callers get "pool exhausted" — an error that points away from the real cause.

Fix: when the session is handed out from a pool, skip the between-attempt sleeps (the slot is still held, but the hold time drops to the connect+handshake attempts), or shorten them. Standalone sessions keep the current C#-style pacing.