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。

Tests/EventBusSubscriptionTests.cs

@@ -0,0 +1,94 @@
+using NUnit.Framework;
+using UnityEngine;
+
+namespace ShrinkEventBus.Tests
+{
+    [TestFixture]
+    public sealed class EventBusSubscriptionTests
+    {
+        private sealed class SampleEvent : EventBase
+        {
+            public int Value { get; set; }
+        }
+
+        [SetUp]
+        public void SetUp()
+        {
+            EventBus.UnregisterAllEvents();
+        }
+
+        [TearDown]
+        public void TearDown()
+        {
+            EventBus.UnregisterAllEvents();
+        }
+
+        [Test]
+        public void SubscribeEvent_Dispose_RemovesOnlyOwnedSubscription()
+        {
+            var firstHits = 0;
+            var secondHits = 0;
+
+            using var first = EventBus.SubscribeEvent<SampleEvent>(_ => firstHits++);
+            using var second = EventBus.SubscribeEvent<SampleEvent>(_ => secondHits++);
+
+            EventBus.TriggerEvent(new SampleEvent());
+            Assert.AreEqual(1, firstHits);
+            Assert.AreEqual(1, secondHits);
+
+            first.Dispose();
+
+            EventBus.TriggerEvent(new SampleEvent());
+            Assert.AreEqual(1, firstHits);
+            Assert.AreEqual(2, secondHits);
+        }
+
+        [Test]
+        public void ActiveSubscriptionSnapshot_ContainsExpectedMetadata()
+        {
+            using var subscription = EventBus.SubscribeEvent<SampleEvent>(_ => { }, EventPriority.HIGH, true);
+
+            var snapshots = EventBus.GetActiveSubscriptionsSnapshot();
+
+            Assert.AreEqual(1, snapshots.Count);
+            Assert.AreEqual(subscription.SubscriptionId, snapshots[0].SubscriptionId);
+            Assert.AreEqual(typeof(SampleEvent), snapshots[0].EventType);
+            Assert.AreEqual(EventPriority.HIGH, snapshots[0].Priority);
+            Assert.IsTrue(snapshots[0].ReceiveCanceled);
+            Assert.IsFalse(string.IsNullOrWhiteSpace(snapshots[0].MethodName));
+        }
+
+        [Test]
+        public void RegisterEvent_StillWorksWithoutDisposableSubscription()
+        {
+            var hits = 0;
+
+            void Handler(SampleEvent evt)
+            {
+                hits += evt.Value;
+            }
+
+            EventBus.RegisterEvent<SampleEvent>(Handler);
+            EventBus.TriggerEvent(new SampleEvent { Value = 3 });
+
+            Assert.AreEqual(3, hits);
+
+            EventBus.UnregisterEvent<SampleEvent>(Handler);
+            EventBus.TriggerEvent(new SampleEvent { Value = 5 });
+
+            Assert.AreEqual(3, hits);
+        }
+
+        [Test]
+        public void ActiveSubscriptionSnapshot_EmptyAfterDispose()
+        {
+            var subscription = EventBus.SubscribeEvent<SampleEvent>(_ => Debug.Log("noop"));
+            subscription.Dispose();
+
+            var snapshots = EventBus.GetActiveSubscriptionsSnapshot();
+
+            Assert.AreEqual(0, snapshots.Count);
+            Assert.IsTrue(subscription.IsDisposed);
+        }
+    }
+}