Cut over the window to Explorer.Host.exe so only the host writes the index.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/Explorer.FileOperations.Tests/FolderSyncServiceTests.cs

@@ -109,12 +109,14 @@ public class FolderSyncServiceTests
                 store,
                 volumes,
                 NullLogger<TransferQueue>.Instance);
+            var mutations = new LocalIndexMutations(store);
             var ops = new FileOperationService(queue, shell, enumerator);
             var env = new SyncEnv(root);
             var sources = new SourceManager(store, volumes, env, new SystemClock(), NullLogger<SourceManager>.Instance);
             var sync = new FolderSyncService(
                 new FolderSyncPlanner(),
                 store,
+                mutations,
                 sources,
                 ops,
                 volumes,