fix(visualizer): lift zoom slider out of fixed backdrop's stacking context so it receives pointer events again (P10 W1)

DeepDrftPublic.Client/Controls/MixWaveformVisualizer.razor

@@ -9,20 +9,25 @@
 
 <div class="mix-waveform-bg">
     <canvas @ref="_canvas" class="mix-waveform-canvas"></canvas>
-
-    @* Viewing control only — never a seek surface. Hidden until a datum is present. *@
-    @if (_hasDatum)
-    {
-        <div class="mix-waveform-zoom">
-            <MudSlider T="double"
-                       Value="@ZoomFraction"
-                       ValueChanged="@OnZoomFractionChanged"
-                       Min="0"
-                       Max="1"
-                       Step="0.001"
-                       Size="Size.Small"
-                       Color="Color.Primary"
-                       aria-label="Waveform zoom" />
-        </div>
-    }
 </div>
+
+@* Viewing control only — never a seek surface. Hidden until a datum is present.
+   Deliberately a SIBLING of .mix-waveform-bg, not a child: the backdrop is position:fixed and so
+   forms its own stacking context, which would trap any descendant below the page's z-index:1
+   foreground (.mix-detail-foreground) and let that foreground swallow the slider's pointer events.
+   As a top-level sibling with its own z-index, the slider stacks above the foreground and stays
+   draggable. *@
+@if (_hasDatum)
+{
+    <div class="mix-waveform-zoom">
+        <MudSlider T="double"
+                   Value="@ZoomFraction"
+                   ValueChanged="@OnZoomFractionChanged"
+                   Min="0"
+                   Max="1"
+                   Step="0.001"
+                   Size="Size.Small"
+                   Color="Color.Primary"
+                   aria-label="Waveform zoom" />
+    </div>
+}

DeepDrftPublic.Client/Controls/MixWaveformVisualizer.razor.cs

@@ -180,6 +180,7 @@ public partial class MixWaveformVisualizer : ComponentBase, IAsyncDisposable
     private async Task OnZoomFractionChanged(double fraction)
     {
         ZoomState.VisibleSeconds = MixZoomMapping.FractionToSeconds(fraction);
+        DebugLog($"zoom slider changed — raw fraction={fraction:F3} → visibleSeconds={ZoomState.VisibleSeconds:F3}s; pushing setZoom (handle={(_handle is null ? "null" : "ready")}).");
         await PushZoomAsync();
         StateHasChanged();
     }

DeepDrftPublic.Client/Controls/MixWaveformVisualizer.razor.css

@@ -21,13 +21,18 @@
 }
 
 /* Zoom slider — a small viewing control pinned to the top-right, clear of the player bar at
-   the bottom and the nav bar at the top. Pointer events are re-enabled here only (the backdrop
-   stays inert), and it is never a seek surface. top: 5rem sits just below the fixed nav bar
-   (~4.5rem tall) so neither the expanded player bar nor the nav occludes it. */
+   the bottom and the nav bar at the top. It is never a seek surface. top: 5rem sits just below the
+   fixed nav bar (~4.5rem tall) so neither the expanded player bar nor the nav occludes it.
+
+   position: fixed (not absolute) because the slider is now a top-level sibling of the backdrop, not
+   a child of it — see the comment in the .razor. z-index: 10 lifts it above the page foreground
+   (.mix-detail-foreground, z-index: 1) so the foreground can't intercept its pointer events; that
+   occlusion was the resolution-slider regression. */
 .mix-waveform-zoom {
-    position: absolute;
+    position: fixed;
     right: 1.5rem;
     top: 5rem;
+    z-index: 10;
     width: 180px;
     max-width: 40vw;
     pointer-events: auto;