feat: declare every protocol method's direction and enforce it in the router; add the zero-trust design [CI]

Methods, roles and binary channels are declared in one table per plane (node and peer). RpcRouter checks direction, kind and role when handlers are registered, when messages arrive (fleet_protocol_violation, disconnect after repeated violations) and before sending. NodeConnection is split by responsibility.

backend/tests/MoShiro.TestSupport/ProbeSimulator.cs

@@ -313,7 +313,7 @@ public sealed class ProbeSimulator : IAsyncDisposable
     }
 
     private RpcRouter<ProbeSimulator> BuildRouter() =>
-        new RpcRouter<ProbeSimulator>()
+        new RpcRouter<ProbeSimulator>(RpcSide.Dialer, MoShiroMethodTable.Table)
             .On(
                 FleetMethods.StateSync,
                 FleetRpcContext.Default.StateSyncParams,