Fix missing disposal of instances in the Agent

Agent/Phantom.Agent.Services/AgentServices.cs

@@ -33,6 +33,8 @@ public sealed class AgentServices {
 		Logger.Information("Stopping services...");
 		
 		await InstanceSessionManager.StopAll();
+		InstanceSessionManager.Dispose();
+		
 		await TaskManager.Stop();
 		
 		Logger.Information("Services stopped.");

Agent/Phantom.Agent.Services/Instances/Instance.cs

@@ -174,10 +174,10 @@ sealed class Instance : IDisposable {
 	}
 
 	public void Dispose() {
+		stateTransitioningActionSemaphore.Dispose();
+		
 		if (currentState is IDisposable disposable) {
 			disposable.Dispose();
 		}
-
-		stateTransitioningActionSemaphore.Dispose();
 	}
 }

Agent/Phantom.Agent.Services/Instances/InstanceSessionManager.cs

@@ -138,15 +138,24 @@ sealed class InstanceSessionManager : IDisposable {
 		await semaphore.WaitAsync(CancellationToken.None);
 		try {
 			await Task.WhenAll(instances.Values.Select(static instance => instance.StopAndWait(TimeSpan.FromSeconds(30))));
-			instances.Clear();
+			DisposeAllInstances();
 		} finally {
 			semaphore.Release();
 		}
 	}
 
 	public void Dispose() {
+		DisposeAllInstances();
 		minecraftServerExecutables.Dispose();
 		shutdownCancellationTokenSource.Dispose();
 		semaphore.Dispose();
 	}
+
+	private void DisposeAllInstances() {
+		foreach (var (_, instance) in instances) {
+			instance.Dispose();
+		}
+
+		instances.Clear();
+	}
 }