perf: reduce diagnostics and queued dispatch allocations in 2.3.2

Samples~/DotNetConsole/Program.cs

@@ -0,0 +1,40 @@
+using ShrinkEventBus;
+
+using var host = new ShrinkEventBusHost();
+var bus = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
+var subscriber = new OrderSubscriber();
+using var binding = host.Attach(subscriber);
+var diagnostics = 0;
+using var observation = EventBus.ObserveDiagnostics(_ => diagnostics++);
+
+bus.Post(new OrderPlaced(2));
+await bus.PostAsync(new OrderPlaced(3));
+if (subscriber.Total != 5 || diagnostics != 2)
+    throw new InvalidOperationException("Generated subscription or diagnostics failed.");
+
+var workerKey = new ShrinkBusKey("worker", "orders");
+var worker = host.CreateBus(workerKey, ShrinkBusOptions.DedicatedThread());
+var workerSubscriber = new OrderSubscriber();
+using var workerBinding = host.Attach(workerSubscriber, workerKey);
+await worker.PostAsync(new OrderPlaced(7));
+if (workerSubscriber.Total != 7)
+    throw new InvalidOperationException("Dedicated-thread delivery failed.");
+
+binding.Dispose();
+bus.Post(new OrderPlaced(10));
+if (subscriber.Total != 5)
+    throw new InvalidOperationException("Unsubscribe failed.");
+
+await host.ShutdownAsync();
+Console.WriteLine("EVENTBUS_CONSOLE_PASS: sync, async, diagnostics, worker, unsubscribe");
+
+public readonly record struct OrderPlaced(int Amount) : IShrinkEvent;
+
+[ShrinkEventSubscriber]
+public sealed partial class OrderSubscriber
+{
+    public int Total { get; private set; }
+
+    [ShrinkSubscribe]
+    private void OnOrder(OrderPlaced order) => Total += order.Amount;
+}