Add Git overlay, operation tools, and virtualized preview so large folders stay responsive.

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

src/Explorer.FileOperations/OperationAvailability.cs

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+using Explorer.Domain;
+using Explorer.Domain.Abstractions;
+
+namespace Explorer.FileOperations;
+
+internal static class OperationAvailability
+{
+    public static bool IsReady(IVolumeService volumes, TransferJob job)
+    {
+        foreach (var path in PathsToCheck(job))
+        {
+            if (!IsVolumeReachable(volumes, path))
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    public static IEnumerable<string> PathsToCheck(TransferJob job)
+    {
+        switch (job.Op)
+        {
+            case TransferOp.Delete:
+                if (job.AdditionalSources.Count > 0)
+                {
+                    foreach (var src in job.AdditionalSources)
+                    {
+                        yield return src;
+                    }
+
+                    yield break;
+                }
+
+                foreach (var src in job.SourcePath.Split('|', StringSplitOptions.RemoveEmptyEntries))
+                {
+                    yield return src;
+                }
+
+                yield break;
+            case TransferOp.Copy:
+            case TransferOp.Move:
+            case TransferOp.Rename:
+            case TransferOp.Extract:
+            case TransferOp.Compress:
+            case TransferOp.AddToArchive:
+                if (!string.IsNullOrWhiteSpace(job.DestinationPath))
+                {
+                    yield return PathRules.Parent(job.DestinationPath);
+                }
+
+                yield break;
+            case TransferOp.VerifyArchive:
+                yield return job.SourcePath;
+                yield break;
+            case TransferOp.EmptyRecycleBin:
+                yield break;
+        }
+    }
+
+    public static bool IsVolumeReachable(IVolumeService volumes, string path)
+    {
+        if (string.IsNullOrWhiteSpace(path))
+        {
+            return true;
+        }
+
+        if (volumes.IsPathReachable(path))
+        {
+            return true;
+        }
+
+        var root = PathRules.VolumeRoot(path);
+        if (string.IsNullOrWhiteSpace(root))
+        {
+            return false;
+        }
+
+        if (!string.Equals(root, path, StringComparison.OrdinalIgnoreCase) && volumes.IsPathReachable(root))
+        {
+            return true;
+        }
+
+        var slashed = root.EndsWith('\\') ? root : root + "\\";
+        return volumes.IsPathReachable(slashed);
+    }
+}