chore: initialize standalone UPM package

Tests/MockStorageProvider.cs

@@ -0,0 +1,54 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using Cysharp.Threading.Tasks;
+
+namespace ShrinkDataSaver.Tests
+{
+    /// <summary>
+    /// 内存模拟存储，用于单元测试，无需文件 I/O。
+    /// </summary>
+    public class MockStorageProvider : IStorageProvider
+    {
+        private readonly Dictionary<string, byte[]> _store = new();
+
+        public UniTask WriteAsync(string path, byte[] data, CancellationToken ct = default)
+        {
+            _store[NormalizePath(path)] = data;
+            return UniTask.CompletedTask;
+        }
+
+        public UniTask<byte[]> ReadAsync(string path, CancellationToken ct = default)
+        {
+            var key = NormalizePath(path);
+            if (!_store.TryGetValue(key, out var data))
+                throw new FileNotFoundException($"MockStorage: {key}");
+            return UniTask.FromResult(data);
+        }
+
+        public UniTask<bool> ExistsAsync(string path, CancellationToken ct = default)
+            => UniTask.FromResult(_store.ContainsKey(NormalizePath(path)));
+
+        public UniTask DeleteAsync(string path, CancellationToken ct = default)
+        {
+            _store.Remove(NormalizePath(path));
+            return UniTask.CompletedTask;
+        }
+
+        public UniTask<string[]> ListAsync(string prefix = "", CancellationToken ct = default)
+        {
+            var norm = NormalizePath(prefix);
+            var results = _store.Keys
+                .Where(k => string.IsNullOrEmpty(norm) || k.StartsWith(norm))
+                .ToArray();
+            return UniTask.FromResult(results);
+        }
+
+        public void Clear() => _store.Clear();
+        public int Count => _store.Count;
+
+        private static string NormalizePath(string path)
+            => path.Replace('\\', '/');
+    }
+}