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

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

tests/Explorer.Hosting.Tests/WorkbenchPipeTests.cs

@@ -14,7 +14,7 @@ public class WorkbenchPipeTests
         var indexing = new FakeIndexing();
         var transfers = new FakeTransfers();
         var server = new WorkbenchPipeServer(
-            new WorkbenchHost(indexing, transfers),
+            new WorkbenchHost(indexing, transfers, new StubSources(), new StubMutations()),
             new WorkbenchIpcOptions { PipeName = "ew-test" },
             NullLogger<WorkbenchPipeServer>.Instance);
 
@@ -31,13 +31,23 @@ public class WorkbenchPipeTests
 
         var paused = server.Handle(new IpcEnvelope { V = WorkbenchIpc.ProtocolVersion, Op = "Transfers.IsPaused" });
         Assert.True(paused.Paused);
+
+        var copy = server.Handle(new IpcEnvelope
+        {
+            V = WorkbenchIpc.ProtocolVersion,
+            Op = "Transfers.EnqueueCopy",
+            Paths = ["C:\\a.txt"],
+            Dest = "D:\\"
+        });
+        Assert.True(copy.Ok);
+        Assert.Equal(@"D:\", transfers.CopiedDest);
     }
 
     [Fact]
     public void Handle_rejects_other_protocol_versions()
     {
         var server = new WorkbenchPipeServer(
-            new WorkbenchHost(new FakeIndexing(), new FakeTransfers()),
+            new WorkbenchHost(new FakeIndexing(), new FakeTransfers(), new StubSources(), new StubMutations()),
             new WorkbenchIpcOptions(),
             NullLogger<WorkbenchPipeServer>.Instance);
         var reply = server.Handle(new IpcEnvelope { V = 99, Op = "Ping" });
@@ -72,5 +82,37 @@ public class WorkbenchPipeTests
         public void ClearFinished() { }
         public bool MoveUp(long jobId) => false;
         public bool MoveDown(long jobId) => false;
+        public string? CopiedDest { get; private set; }
+        public Task EnqueueCopyAsync(IReadOnlyList<string> sources, string destinationDirectory, CancellationToken cancellationToken = default)
+        {
+            CopiedDest = destinationDirectory;
+            return Task.CompletedTask;
+        }
+    }
+
+    private sealed class StubSources : ISourceHost
+    {
+        public Task RefreshAsync(CancellationToken cancellationToken = default) => Task.CompletedTask;
+        public Task<Source> AddUncAsync(string path, CancellationToken cancellationToken = default)
+            => Task.FromResult(new Source { StableKey = "x", DisplayName = path });
+        public Task<Source?> EnsureForPathAsync(string path, CancellationToken cancellationToken = default)
+            => Task.FromResult<Source?>(null);
+        public Task<bool> ForgetAsync(string path, CancellationToken cancellationToken = default)
+            => Task.FromResult(false);
+    }
+
+    private sealed class StubMutations : IIndexMutations
+    {
+        public Task<long> UpsertSyncProfileAsync(SyncProfile profile, CancellationToken cancellationToken = default)
+            => Task.FromResult(1L);
+        public Task DeleteSyncProfileAsync(long id, CancellationToken cancellationToken = default) => Task.CompletedTask;
+        public Task<long> UpsertOperationProfileAsync(OperationProfile profile, CancellationToken cancellationToken = default)
+            => Task.FromResult(1L);
+        public Task DeleteOperationProfileAsync(long id, CancellationToken cancellationToken = default) => Task.CompletedTask;
+        public Task<long> CreateRenameBatchAsync(IReadOnlyList<RenameBatchItem> items, CancellationToken cancellationToken = default)
+            => Task.FromResult(1L);
+        public Task MarkRenameBatchUndoneAsync(long id, CancellationToken cancellationToken = default) => Task.CompletedTask;
+        public Task EnqueueHashCollisionsAsync(long? sourceId, CancellationToken cancellationToken = default) => Task.CompletedTask;
+        public Task UpsertRelationAsync(FileRelation relation, CancellationToken cancellationToken = default) => Task.CompletedTask;
     }
 }