CacheManager: Remove back-compat DriveRoots check that no longer exists. CacheData now uses single DriveRoot string matching Rust.

FastSeekWpf/Core/CacheManager.cs

@@ -48,14 +48,7 @@ public static class CacheManager
             byte[] compressed = File.ReadAllBytes(CachePath);
             byte[] bytes = LZ4Pickler.Unpickle(compressed);
             string json = Encoding.UTF8.GetString(bytes);
-            var cache = JsonSerializer.Deserialize<CacheData>(json, JsonOptions);
-            // Back-compat: single DriveRoot → DriveRoots list
-            if (cache != null && cache.DriveRoots == null || cache!.DriveRoots.Count == 0)
-            {
-                // This is the old format — can't use it, need full rescan
-                return null;
-            }
-            return cache;
+            return JsonSerializer.Deserialize<CacheData>(json, JsonOptions);
         }
         catch
         {