fix(dotnet): Add AOT-safe SetForegroundSessionRequest for SetForegroundSessionIdAsync()

- Replace the anonymous `new { sessionId }` with `new SetForegroundSessionRequest(sessionId)`

This fixes the runtime `System.Text.Json` metadata failure when `SetForegroundSessionIdAsync()` is used with source-generated serialization.

Author: Encryptoid

dotnet/src/Client.cs

@@ -942,7 +942,7 @@ public async Task SetForegroundSessionIdAsync(string sessionId, CancellationToke
         var connection = await EnsureConnectedAsync(cancellationToken);
 
         var response = await InvokeRpcAsync<SetForegroundSessionResponse>(
-            connection.Rpc, "session.setForeground", [new { sessionId }], cancellationToken);
+            connection.Rpc, "session.setForeground", [new SetForegroundSessionRequest(sessionId)], cancellationToken);
 
         if (!response.Success)
         {
@@ -1753,6 +1753,9 @@ internal record GetSessionMetadataRequest(
     internal record GetSessionMetadataResponse(
         SessionMetadata? Session);
 
+    internal record SetForegroundSessionRequest(
+        string SessionId);
+
     internal record UserInputRequestResponse(
         string Answer,
         bool WasFreeform);
@@ -1871,6 +1874,7 @@ private static LogLevel MapLevel(TraceEventType eventType)
     [JsonSerializable(typeof(SessionCapabilities))]
     [JsonSerializable(typeof(SessionUiCapabilities))]
     [JsonSerializable(typeof(SessionMetadata))]
+    [JsonSerializable(typeof(SetForegroundSessionRequest))]
     [JsonSerializable(typeof(SystemMessageConfig))]
     [JsonSerializable(typeof(SystemMessageTransformRpcResponse))]
     [JsonSerializable(typeof(CommandWireDefinition))]