feat: 重构事件总线为可实例化架构并发布 1.3.0

- 新增 IShrinkEventBus、ShrinkEventBusBuilder 与 ShrinkEventBusInstance，支持独立 bus、异常策略、启动开关、类型校验和按 phase 派发
- 新增 SubscribeEvent 可释放订阅句柄与订阅快照接口，保留 EventBus 静态门面并委托到默认实例
- 重构监听列表为父子事件链共享锁与快照缓存，支持父事件监听子事件、跨父子数字优先级归并和防御性快照拷贝
- 优化 EventBase 元数据缓存、懒生成 EventId、派发快照挂接与对象池双重归还保护，移除旧 EventCache 热路径
- 恢复本地 ILPostProcessor 兜底并生成静态订阅注册表，避免共享 CodeGen 覆盖外程序集自动注册失效
- 改进事件查看器、Benchmark、README 与 CHANGELOG，并新增 Dispatch/Priority/Registration/Subscription 测试覆盖核心行为

BREAKING CHANGE: 移除 EventBase.GetListenerList()，int 数字优先级重载不再提供默认值，数字优先级 0 现在映射为 NORMAL。

Runtime/ShrinkEventBusBuilder.cs

@@ -0,0 +1,76 @@
+#nullable enable
+using System;
+
+namespace ShrinkEventBus
+{
+    public sealed class ShrinkEventBusBuilder
+    {
+        internal IShrinkEventExceptionHandler? ExceptionHandler { get; private set; }
+        internal ShrinkEventExceptionHandlingMode ExceptionHandlingMode { get; private set; } =
+            ShrinkEventExceptionHandlingMode.LogAndContinue;
+        internal Action<Type>? EventClassChecker { get; private set; }
+        internal bool StartShutdownEnabled { get; private set; }
+        internal bool CheckTypesOnDispatchEnabled { get; private set; }
+        internal bool AllowPerPhaseDispatchEnabled { get; private set; }
+
+        public ShrinkEventBusBuilder SetExceptionHandler(IShrinkEventExceptionHandler handler)
+        {
+            ExceptionHandler = handler ?? throw new ArgumentNullException(nameof(handler));
+            return this;
+        }
+
+        public ShrinkEventBusBuilder SetExceptionHandlingMode(ShrinkEventExceptionHandlingMode mode)
+        {
+            ExceptionHandlingMode = mode;
+            return this;
+        }
+
+        public ShrinkEventBusBuilder StartShutdown()
+        {
+            StartShutdownEnabled = true;
+            return this;
+        }
+
+        public ShrinkEventBusBuilder CheckTypesOnDispatch()
+        {
+            CheckTypesOnDispatchEnabled = true;
+            return this;
+        }
+
+        public ShrinkEventBusBuilder AllowPerPhaseDispatch()
+        {
+            AllowPerPhaseDispatchEnabled = true;
+            return this;
+        }
+
+        public ShrinkEventBusBuilder ClassChecker(Action<Type> checker)
+        {
+            if (checker == null)
+                throw new ArgumentNullException(nameof(checker));
+
+            EventClassChecker = EventClassChecker == null
+                ? checker
+                : EventClassChecker + checker;
+            return this;
+        }
+
+        public ShrinkEventBusBuilder MarkerInterface<TMarker>() where TMarker : class
+        {
+            var markerType = typeof(TMarker);
+            if (!markerType.IsInterface)
+                throw new InvalidOperationException($"Marker type {markerType.FullName} must be an interface.");
+
+            return ClassChecker(eventType =>
+            {
+                if (!markerType.IsAssignableFrom(eventType))
+                    throw new ArgumentException(
+                        $"This bus only accepts events assignable to {markerType.FullName}, but got {eventType.FullName}.");
+            });
+        }
+
+        public IShrinkEventBus Build()
+        {
+            return new ShrinkEventBusInstance(this);
+        }
+    }
+}