feat(public): add /cuts/{id} album-detail page

Compose ReleaseDetailScaffold via Header + BodyContent slots for the Cut
album view: left meta + Play/Share, right theme-bordered cover, TrackNumber-
ordered track list with per-row play. CutDetailBase carries the multi-track
prerender bridge.

DeepDrftPublic.Client/Controls/ReleaseDetailScaffold.razor

@@ -13,20 +13,30 @@
 
     @TopContent
 
-    <MudStack Row AlignItems="AlignItems.Start" Justify="Justify.SpaceBetween" Style="margin: 2rem 0 1.5rem;">
-        <div class="deepdrft-track-detail-masthead">
-            <MudText Typo="Typo.h3">@Title</MudText>
-            <MudText Typo="Typo.h6" Color="Color.Primary">@Artist</MudText>
-        </div>
+    @* The header region. A composer that wants the default masthead+play row supplies nothing; one
+       that needs a different arrangement (e.g. the Cut album's left-meta / right-cover split) supplies
+       its own Header fragment. Layout variance rides this slot, never a boolean flag (Phase 9 §5.3). *@
+    @if (Header is not null)
+    {
+        @Header
+    }
+    else
+    {
+        <MudStack Row AlignItems="AlignItems.Start" Justify="Justify.SpaceBetween" Style="margin: 2rem 0 1.5rem;">
+            <div class="deepdrft-track-detail-masthead">
+                <MudText Typo="Typo.h3">@Title</MudText>
+                <MudText Typo="Typo.h6" Color="Color.Primary">@Artist</MudText>
+            </div>
 
-        @* Play only makes sense once a playable track is resolved. *@
-        @if (Track is not null)
-        {
-            <MudStack Row AlignItems="AlignItems.Center" Spacing="1">
-                <PlayStateIcon Track="@Track" Size="Size.Large" Color="Color.Secondary" OnToggle="@PlayTrack" />
-            </MudStack>
-        }
-    </MudStack>
+            @* Play only makes sense once a playable track is resolved. *@
+            @if (Track is not null)
+            {
+                <MudStack Row AlignItems="AlignItems.Center" Spacing="1">
+                    <PlayStateIcon Track="@Track" Size="Size.Large" Color="Color.Secondary" OnToggle="@PlayTrack" />
+                </MudStack>
+            }
+        </MudStack>
+    }
 
     @Hero
 
@@ -38,7 +48,12 @@
         </div>
     }
 
-    @if (Track is not null)
+    @* Multi-track body region (the Cut album's track list). Single-track media leave it null. *@
+    @BodyContent
+
+    @* The default share row is bound to the single resolved track. A composer that owns its own share
+       affordance (the Cut header carries Play + Share inline) suppresses it via ShowShareRow. *@
+    @if (Track is not null && ShowShareRow)
     {
         <div class="deepdrft-share-row">
             <SharePopover EntryKey="@Track.EntryKey" />

DeepDrftPublic.Client/Controls/ReleaseDetailScaffold.razor.cs

@@ -31,9 +31,24 @@ public partial class ReleaseDetailScaffold : ComponentBase
     /// </summary>
     [Parameter] public RenderFragment? TopContent { get; set; }
 
+    /// <summary>
+    /// Optional replacement for the header region (masthead + play affordance). When null, the
+    /// scaffold renders its default masthead+play row wired to <see cref="PlayTrack"/>. A composer
+    /// that needs a different header arrangement (e.g. the Cut album's left-meta / right-cover split
+    /// with its own Play/Share buttons) supplies this — layout variance rides the slot, never a
+    /// boolean flag (Phase 9 §5.3).
+    /// </summary>
+    [Parameter] public RenderFragment? Header { get; set; }
+
     /// <summary>Medium-specific hero visual (cover art, hero image, or waveform background).</summary>
     [Parameter] public RenderFragment? Hero { get; set; }
 
+    /// <summary>
+    /// Optional body region rendered below the meta block — the Cut album's multi-track listing.
+    /// Single-track media leave it null.
+    /// </summary>
+    [Parameter] public RenderFragment? BodyContent { get; set; }
+
     /// <summary>Optional medium-specific metadata block, rendered under a divider when present.</summary>
     [Parameter] public RenderFragment? MetaContent { get; set; }
 
@@ -44,6 +59,13 @@ public partial class ReleaseDetailScaffold : ComponentBase
     /// </summary>
     [Parameter] public bool ShowMeta { get; set; } = true;
 
+    /// <summary>
+    /// Gate for the default track-keyed share row at the foot of the scaffold. A composer that owns
+    /// its own share affordance (the Cut header carries Play + Share inline) sets this false to
+    /// suppress the duplicate. Defaults to shown.
+    /// </summary>
+    [Parameter] public bool ShowShareRow { get; set; } = true;
+
     private async Task PlayTrack()
     {
         if (Track is null || PlayerService is null) return;