Merge p9-w6-t2-batchedit-collapse into dev (9.6.B)

DeepDrftManager/Components/Pages/Tracks/BatchEdit.razor

@@ -53,15 +53,15 @@
             </MudStack>
         }
 
+        @* Session/Mix are single-track releases (§9.3): suppress the add-track affordance and keep the
+           list collapsed to one row — OnMediumChanged trims rows 2..n when the medium switches to a
+           single-track medium, mirroring BatchUpload's same-named collapse. Cut keeps the full list. *@
         <MudGrid>
             <MudItem xs="12" md="5">
-                @* The medium write path persists _medium on save (9.5.B). BatchEdit still shows the full
-                   multi-track list for every medium; collapsing to a single-track slot for Session/Mix
-                   (matching BatchUpload's @if (_medium == ReleaseMedium.Cut) guard) is deferred form-shape
-                   work, not part of the write-path wiring. *@
                 <BatchTrackList Tracks="_tracks"
                                 @bind-SelectedIndex="_selectedIndex"
                                 Disabled="_saving"
+                                AllowNewTracks="@(_medium == ReleaseMedium.Cut)"
                                 OnWavFilesSelected="HandleWavFilesSelected"
                                 OnMoveUp="MoveUp"
                                 OnMoveDown="MoveDown"
@@ -135,7 +135,20 @@
     // The medium selector drives ReleaseType visibility and is persisted on save: every UpdateAsync /
     // UploadTrackAsync call below passes _medium, and PUT api/track/meta resets ReleaseType to its
     // default server-side for a non-Cut medium.
-    private void OnMediumChanged(ReleaseMedium medium) => _medium = medium;
+    //
+    // Switching to a single-track medium (Session/Mix) collapses any multi-track list to the first row
+    // so the single-track invariant (§9.3) holds before save — the same collapse BatchUpload.OnMediumChanged
+    // performs. Dropping rows 2..n is an in-memory trim only; existing tracks are not deleted server-side
+    // (RemoveRow owns deletion), so the hidden rows simply fall out of this edit session.
+    private void OnMediumChanged(ReleaseMedium medium)
+    {
+        _medium = medium;
+        if (medium != ReleaseMedium.Cut && _tracks.Count > 1)
+        {
+            _tracks.RemoveRange(1, _tracks.Count - 1);
+            _selectedIndex = _tracks.Count > 0 ? 0 : -1;
+        }
+    }
 
     protected override async Task OnInitializedAsync()
     {
@@ -181,6 +194,11 @@
             Status = BatchRowStatus.Queued
         }).ToList();
 
+        if (_medium != ReleaseMedium.Cut && _tracks.Count > 1)
+        {
+            _tracks.RemoveRange(1, _tracks.Count - 1);
+        }
+
         _selectedIndex = _tracks.Count > 0 ? 0 : -1;
         _loading = false;
     }