Joseph Doherty
285ef64160
A client that opens a session and vanishes before it ever streams (e.g. OtOpcUa's GalaxyDriver on a failed start) pinned a session slot and a live x86 worker for the full DefaultLeaseSeconds (1800 s), because detach-grace only applies to sessions that once had a subscriber. MxGateway:Sessions:UnattachedSessionGraceSeconds (int, default 0 = off, validated >= 0) makes the existing lease sweep reap a Ready session that has never attached an event subscriber once it has been idle (no unary activity) for the window, with the close reason unattached-grace-expired. Ready-only, idle-from-last-activity and first-subscriber-cancels keep it from catching slow starts or unary-only clients. GatewaySession.ExtendLease had no production callers and did not fit the rule, so it is removed; tests move leases through TouchClientActivity.