8.L: collapse release/track name for single-track media (Session, Mix)

BatchTrackDetail gains ShowTrackName parameter (default true); BatchUpload removes the
Track Name input on the single-track path; BatchEdit suppresses it there too. Both sync
_tracks[0].TrackName = _albumName on submit/save so names can never diverge. Cut path
unchanged.

DeepDrftManager/Components/Pages/Tracks/BatchTrackDetail.razor

@@ -5,14 +5,17 @@
 else
 {
     <MudStack Spacing="4">
-        <MudTextField Value="SelectedTrack.TrackName"
-                      ValueChanged="@((string v) => TrackNameChanged.InvokeAsync(v))"
-                      T="string"
-                      Label="Track Name"
-                      Required="true"
-                      RequiredError="Track Name is required"
-                      Variant="Variant.Outlined"
-                      Disabled="Disabled" />
+        @if (ShowTrackName)
+        {
+            <MudTextField Value="SelectedTrack.TrackName"
+                          ValueChanged="@((string v) => TrackNameChanged.InvokeAsync(v))"
+                          T="string"
+                          Label="Track Name"
+                          Required="true"
+                          RequiredError="Track Name is required"
+                          Variant="Variant.Outlined"
+                          Disabled="Disabled" />
+        }
 
         @if (SelectedTrack.Id.HasValue)
         {
@@ -46,6 +49,12 @@ else
     [Parameter] public BatchRowModel? SelectedTrack { get; set; }
     [Parameter] public bool Disabled { get; set; }
     [Parameter] public EventCallback<string> TrackNameChanged { get; set; }
+    /// <summary>
+    /// When false (single-track Session/Mix), the Track Name field is suppressed — the name is
+    /// derived from the Release Name by the parent form and never entered independently.
+    /// Defaults to true so the Cut multi-track path is unchanged.
+    /// </summary>
+    [Parameter] public bool ShowTrackName { get; set; } = true;
 
     private static string FormatBytes(long bytes)
     {