feat: 公开宿主组合加载 API、Forge 风格依赖版本区间与加载顺序、程序集解析策略

- ShrinkModComponentDiscovery.Discover 公开：只发现、不执行生命周期
- ShrinkModLoader.LoadComposed / ShrinkModCordisRuntime.ApplyComposedAsync：宿主提供元数据组合加载，支持纯数据包与 IShrinkModWrapper 公开真实实例
- 公开 TryAttachEventBusInstance，随生命周期逆操作释放
- 依赖新增 VersionRange（Maven/Forge 区间语法）与 Ordering（Before/After）
- AssemblyResolvePolicy 可限制跨模组程序集解析

Tools~/HostTests/Runtime/UnityTestShim.cs

@@ -0,0 +1,49 @@
+// Minimal engine boundary for .NET lifecycle tests; not a Unity runtime replacement.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Reflection;
+
+namespace UnityEngine
+{
+    public class Object
+    {
+        public static implicit operator bool(Object value) => value != null;
+        public static void DestroyImmediate(Object value)
+        {
+            if (value is GameObject go) foreach (var component in go.Components)
+                component.GetType().GetMethod("OnDestroy", BindingFlags.NonPublic | BindingFlags.Instance)?.Invoke(component, null);
+        }
+        public static void Destroy(Object value) => DestroyImmediate(value);
+        public static void DontDestroyOnLoad(Object value) { }
+    }
+    public class ScriptableObject : Object { public static T CreateInstance<T>() where T : ScriptableObject, new() => new T(); }
+    public class MonoBehaviour : Object { public GameObject gameObject; }
+    public class GameObject : Object
+    {
+        internal readonly List<MonoBehaviour> Components = new();
+        public GameObject(string name) { }
+        public T AddComponent<T>() where T : MonoBehaviour, new() { var c = new T { gameObject = this }; Components.Add(c); return c; }
+    }
+    public static class Resources { public static T Load<T>(string path) where T : Object => null; }
+    public static class Application { public static string persistentDataPath => System.IO.Path.GetTempPath(); public static bool isPlaying => false; }
+    public static class Time { private static readonly Stopwatch Clock = Stopwatch.StartNew(); public static float realtimeSinceStartup => (float)Clock.Elapsed.TotalSeconds; }
+    public static class Mathf { public static float Max(float a, float b) => Math.Max(a, b); }
+    public enum LogType { Error, Assert, Warning, Log, Exception }
+    public static class Debug
+    {
+        public static event Action<LogType, string> Logged;
+        public static void Log(object value) => Logged?.Invoke(LogType.Log, value?.ToString());
+        public static void LogWarning(object value) => Logged?.Invoke(LogType.Warning, value?.ToString());
+        public static void LogError(object value) => Logged?.Invoke(LogType.Error, value?.ToString());
+        public static void LogException(Exception value) => Logged?.Invoke(LogType.Exception, value.ToString());
+    }
+    public class CreateAssetMenuAttribute : Attribute { public string fileName, menuName; }
+    public class HeaderAttribute : Attribute { public HeaderAttribute(string text) { } }
+    public class TooltipAttribute : Attribute { public TooltipAttribute(string text) { } }
+    public class MinAttribute : Attribute { public MinAttribute(float value) { } }
+    public class SerializeField : Attribute { }
+    public class DefaultExecutionOrder : Attribute { public DefaultExecutionOrder(int value) { } }
+    public enum RuntimeInitializeLoadType { SubsystemRegistration, AfterAssembliesLoaded }
+    public class RuntimeInitializeOnLoadMethodAttribute : Attribute { public RuntimeInitializeOnLoadMethodAttribute(RuntimeInitializeLoadType type) { } }
+}