Show folder names immediately and refresh stale index sizes without walking the whole drive.

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

src/Explorer.Application/BackgroundMaintenancePlanner.cs

@@ -0,0 +1,44 @@
+using Explorer.Domain;
+
+namespace Explorer.Application;
+
+public static class BackgroundMaintenancePlanner
+{
+    public static Source? NextLocalScan(
+        IEnumerable<Source> sources,
+        DateTimeOffset utc,
+        IReadOnlySet<long>? alreadyQueued = null)
+    {
+        var cutoff = utc - TimeSpan.FromDays(AppConstants.IdleRescanAfterDays);
+        return EligibleLocal(sources, alreadyQueued)
+            .Where(source => source.Status == SourceStatus.Stale
+                             || source.LastIndexedUtc is null
+                             || source.LastIndexedUtc < cutoff)
+            .OrderBy(source => source.Status == SourceStatus.Stale ? 0 : 1)
+            .ThenBy(source => source.LastIndexedUtc ?? DateTimeOffset.MinValue)
+            .FirstOrDefault();
+    }
+
+    public static Source? NextLocalVerify(
+        IEnumerable<Source> sources,
+        IReadOnlySet<long>? alreadyQueued = null)
+        => EligibleLocal(sources, alreadyQueued)
+            .OrderBy(source => source.Status == SourceStatus.Stale ? 0 : 1)
+            .ThenBy(source => source.LastIndexedUtc ?? DateTimeOffset.MinValue)
+            .FirstOrDefault();
+
+    public static Source? NextHashCollisionSource(
+        IEnumerable<Source> sources,
+        IReadOnlySet<long>? alreadyEnqueued = null)
+        => EligibleLocal(sources, alreadyEnqueued)
+            .OrderBy(source => source.LastIndexedUtc ?? DateTimeOffset.MinValue)
+            .FirstOrDefault();
+
+    private static IEnumerable<Source> EligibleLocal(IEnumerable<Source> sources, IReadOnlySet<long>? skip)
+        => sources.Where(source =>
+            source.Kind == SourceKind.NtfsLocal
+            && source.IsIndexed
+            && source.Status is SourceStatus.Online or SourceStatus.Stale
+            && !string.IsNullOrWhiteSpace(source.LastRootPath)
+            && (skip is null || !skip.Contains(source.Id)));
+}