Fix runtime review findings

docs/GatewayConfiguration.md

@@ -35,6 +35,8 @@ paths, timeouts, queue sizes, enum values, or protocol values are invalid.
       "DefaultCommandTimeoutSeconds": 30,
       "MaxSessions": 64,
       "MaxPendingCommandsPerSession": 128,
+      "DefaultLeaseSeconds": 1800,
+      "LeaseSweepIntervalSeconds": 30,
       "AllowMultipleEventSubscribers": false
     },
     "Events": {
@@ -52,7 +54,8 @@ paths, timeouts, queue sizes, enum values, or protocol values are invalid.
       "ShowTagValues": false
     },
     "Protocol": {
-      "WorkerProtocolVersion": 1
+      "WorkerProtocolVersion": 1,
+      "MaxGrpcMessageBytes": 16777216
     },
     "Galaxy": {
       "ConnectionString": "Server=localhost;Database=ZB;Integrated Security=True;TrustServerCertificate=True;Encrypt=False;",
@@ -107,6 +110,8 @@ to avoid accidental large allocations from malformed or oversized frames.
 | `MxGateway:Sessions:DefaultCommandTimeoutSeconds` | `30` | Default timeout used while the gateway waits for a worker command reply when an open-session request does not provide a positive command timeout. |
 | `MxGateway:Sessions:MaxSessions` | `64` | Maximum number of concurrently open gateway sessions. Session opens reserve a slot atomically before worker creation. |
 | `MxGateway:Sessions:MaxPendingCommandsPerSession` | `128` | Maximum number of pending worker commands for one session. Excess commands fail fast instead of queueing indefinitely. |
+| `MxGateway:Sessions:DefaultLeaseSeconds` | `1800` | Initial session lease and refresh duration. Unary client activity extends the lease by this duration. |
+| `MxGateway:Sessions:LeaseSweepIntervalSeconds` | `30` | Hosted monitor interval for closing expired leases. Active event-stream subscribers keep a session from expiring while the stream remains attached. |
 | `MxGateway:Sessions:AllowMultipleEventSubscribers` | `false` | Controls whether multiple `StreamEvents` subscribers may attach to one session. `true` is rejected until event fan-out is implemented. |
 
 All numeric session options must be greater than zero. The current event stream
@@ -146,6 +151,7 @@ and `RecentSessionLimit` must be greater than or equal to zero.
 | Option | Default | Description |
 |--------|---------|-------------|
 | `MxGateway:Protocol:WorkerProtocolVersion` | `1` | Worker IPC protocol version expected by the gateway and worker. This must match `GatewayContractInfo.WorkerProtocolVersion`. |
+| `MxGateway:Protocol:MaxGrpcMessageBytes` | `16777216` | Public gRPC max send and receive message size in bytes. The same default is used by official clients. The validator allows values from `1024` through `268435456`. |
 
 The protocol option is exposed for diagnostics and explicit deployment
 configuration, not for compatibility negotiation. A mismatch fails validation