feat(cms): Release Archive medium tab strip (ALL · CUTS · SESSIONS · MIXES), retire navigate-away cards

Replace the navigate-away ReleaseArchiveBrowser cards and the redundant top-level Releases
toggle with an in-page MudTabs strip under the Releases mode: ALL (CmsAllReleasesGrid) plus
one enum-driven tab per ReleaseMedium. Sessions/Mixes browsers gain an Embedded flag that
suppresses standalone page chrome when hosted as tab content; CmsCutBrowser is the new
Cut-filtered grid. /tracks/sessions, /tracks/mixes, /tracks/archive stay reachable by URL.

DeepDrftManager/Components/Pages/Tracks/TrackList.razor

@@ -3,6 +3,7 @@
 @page "/tracks/genres"
 @page "/tracks/archive"
 @using DeepDrftManager.Services
+@using DeepDrftModels.Enums
 @inject CmsTrackBrowserViewModel VM
 @inject ICmsTrackService CmsTrackService
 @inject ISnackbar Snackbar
@@ -36,6 +37,9 @@
         }
     </MudStack>
 
+    @* Top-level browse dimension. The former three-way toggle (Tracks / Releases / Release Archive)
+       collapsed to two (§8.A): "Releases" now hosts the in-page medium tab strip below, subsuming both
+       the old Releases grid (as the ALL tab) and the retired Release Archive cards. *@
     <MudToggleGroup T="BrowseMode"
                     Value="VM.Mode"
                     ValueChanged="OnModeChanged"
@@ -45,7 +49,6 @@
                     Class="mb-4">
         <MudToggleItem Value="BrowseMode.Tracks">Tracks</MudToggleItem>
         <MudToggleItem Value="BrowseMode.Albums">Releases</MudToggleItem>
-        <MudToggleItem Value="BrowseMode.Archive">Release Archive</MudToggleItem>
     </MudToggleGroup>
 
     @if (VM.Mode == BrowseMode.Tracks)
@@ -54,15 +57,21 @@
     }
     else if (VM.Mode == BrowseMode.Albums)
     {
-        @* The all-releases grid is now a self-contained component (Phase 9 §8.B): it owns its own load
-           and refresh, so the host renders it with no parameters. The 8.A tab strip hosts this same
-           component as its ALL tab. Genre mode still uses the VM cache below; only album loading moved
-           into the component, so VM.Albums / VM.AlbumsLoading are no longer read here. *@
-        <CmsAllReleasesGrid OnReleasesChanged="OnAlbumsChanged" />
-    }
-    else if (VM.Mode == BrowseMode.Archive)
-    {
-        <ReleaseArchiveBrowser />
+        @* The Release Archive tab strip (§8.A): an ALL tab plus one tab per ReleaseMedium, ALL left-most.
+           The medium tabs are enum-driven — a fourth medium adds a tab automatically; only a label-lookup
+           entry (MediumTabLabels) and a content arm (MediumGrid) are needed, no markup fork. Selecting a
+           tab swaps the grid below in place; no navigation to a separate page occurs. *@
+        <MudTabs Elevation="0" Rounded="true" ApplyEffectsToContainer="true" PanelClass="pt-4">
+            <MudTabPanel Text="ALL">
+                <CmsAllReleasesGrid OnReleasesChanged="OnAlbumsChanged" />
+            </MudTabPanel>
+            @foreach (var medium in Enum.GetValues<ReleaseMedium>())
+            {
+                <MudTabPanel Text="@MediumTabLabels[medium]">
+                    @MediumGrid(medium)
+                </MudTabPanel>
+            }
+        </MudTabs>
     }
     else
     {
@@ -78,6 +87,29 @@
 @code {
     private CmsTrackGrid? _grid;
 
+    // Medium → tab label. The one place medium display text lives for the tab strip; a future medium adds
+    // one entry here and surfaces a tab automatically. Mirrors the extension discipline the retired
+    // ReleaseArchiveBrowser used for its cards. The ALL tab is rendered separately (it is not a medium).
+    private static readonly IReadOnlyDictionary<ReleaseMedium, string> MediumTabLabels =
+        new Dictionary<ReleaseMedium, string>
+        {
+            [ReleaseMedium.Cut] = "CUTS",
+            [ReleaseMedium.Session] = "SESSIONS",
+            [ReleaseMedium.Mix] = "MIXES",
+        };
+
+    // Medium → embedded grid. Each medium's grid is its own component (Cut has no per-row action; Session
+    // carries hero upload; Mix carries waveform generation), so the content dispatch is a per-medium
+    // mapping by nature — but it is a single switch returning a fragment, not a markup fork. The browsers
+    // render Embedded so their standalone page chrome (container, title, back button) is suppressed here.
+    private RenderFragment MediumGrid(ReleaseMedium medium) => medium switch
+    {
+        ReleaseMedium.Cut => @<CmsCutBrowser />,
+        ReleaseMedium.Session => @<CmsSessionBrowser Embedded="true" />,
+        ReleaseMedium.Mix => @<CmsMixBrowser Embedded="true" />,
+        _ => @<MudText Typo="Typo.body1" Class="mt-4">No grid for this medium.</MudText>
+    };
+
     // The all-releases grid refreshes its own list after a delete; this notification lets us invalidate
     // the VM's genre cache so genre counts reflect the deletion on the next switch into Genre mode.
     private void OnAlbumsChanged()
@@ -93,10 +125,12 @@
 
     protected override async Task OnInitializedAsync()
     {
+        // /tracks/archive and /tracks/albums both land on the Releases view (the tab strip); the old
+        // separate Archive mode is retired (§8.A) but the route stays reachable rather than 404ing.
         var uri = NavigationManager.Uri;
         var initial =
             uri.Contains("/tracks/albums", StringComparison.OrdinalIgnoreCase) ? BrowseMode.Albums
-            : uri.Contains("/tracks/archive", StringComparison.OrdinalIgnoreCase) ? BrowseMode.Archive
+            : uri.Contains("/tracks/archive", StringComparison.OrdinalIgnoreCase) ? BrowseMode.Albums
             : uri.Contains("/tracks/genres", StringComparison.OrdinalIgnoreCase) ? BrowseMode.Genres
             : BrowseMode.Tracks;
         await VM.SwitchModeAsync(initial);
@@ -108,7 +142,6 @@
         var path = mode switch
         {
             BrowseMode.Albums => "/tracks/albums",
-            BrowseMode.Archive => "/tracks/archive",
             BrowseMode.Genres => "/tracks/genres",
             _ => "/tracks"
         };