Improve file operations, layout memory, and drive status.

Add a sequential file-operations queue with pause, reorder, and optional auto-clear; persist window size and tree width; show free space; and clear leftover indexing status.

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

tests/Explorer.Application.Tests/SourceManagerTests.cs

@@ -136,6 +136,39 @@ public class SourceManagerTests
         Assert.Null(await store.Entries.GetRootAsync(source.Id));
     }
 
+    [Fact]
+    public async Task Stale_scanning_status_clears_when_no_job_is_running()
+    {
+        var db = Path.Combine(Path.GetTempPath(), "ew-app", Guid.NewGuid().ToString("N"), "index.db");
+        await using var store = new SqliteIndexStore(db, NullLogger<SqliteIndexStore>.Instance);
+        await store.OpenAsync();
+        var volumes = new FakeVolumes
+        {
+            Online =
+            [
+                new VolumeFingerprint
+                {
+                    Kind = SourceKind.NtfsLocal,
+                    RootPath = @"D:\",
+                    DisplayName = "Games (D:)",
+                    VolumeSerial = 42,
+                    CapacityBytes = 1000
+                }
+            ]
+        };
+        var env = new FakeEnv(Path.GetDirectoryName(db)!);
+        var mgr = new SourceManager(store, volumes, env, new SystemClock(), NullLogger<SourceManager>.Instance);
+        await mgr.InitializeAsync();
+        var source = (await store.Sources.GetAllAsync()).Single();
+        await store.Sources.UpdateStatusAsync(source.Id, SourceStatus.Scanning, null);
+        await store.Sources.UpdateIndexedAsync(source.Id, DateTimeOffset.UtcNow, 1);
+
+        await mgr.RefreshOnlineStateAsync();
+        source = (await store.Sources.GetAllAsync()).Single();
+        Assert.Equal(SourceStatus.Online, source.Status);
+        Assert.True(source.IsIndexed);
+    }
+
     [Fact]
     public async Task Forget_removes_unc_from_recents()
     {
@@ -166,6 +199,11 @@ file sealed class FakeVolumes : IVolumeService
             || v.RootPath.Equals(path, StringComparison.OrdinalIgnoreCase));
     }
     public bool IsPathReachable(string path) => Online.Any(v => path.StartsWith(v.RootPath.TrimEnd('\\'), StringComparison.OrdinalIgnoreCase));
+    public VolumeSpace GetSpace(string path)
+    {
+        var fp = Probe(path);
+        return new VolumeSpace(fp?.CapacityBytes, fp?.FreeBytes);
+    }
 }
 
 file sealed class FakeEnv : IAppEnvironment