refactor(12.A): rename Mix* visualizer engine to Waveform* abstraction

DeepDrftPublic.Client/Controls/WaveformVisualizer.razor

@@ -0,0 +1,16 @@
+@namespace DeepDrftPublic.Client.Controls
+
+@* Full-page scrolling waveform background (Phase 9, 8.K). A windowed slice of the track's loudness
+   datum scrolls bottom-to-top, coupled to playback; a zoom slider controls the visible time-span (and
+   so the apparent scroll speed, Guitar-Hero style). Strictly read-only: it self-fetches its datum from
+   ReleaseEntryKey, takes playback as one-way input only, and never seeks or writes back. The rAF loop and all
+   scroll/zoom/compositing math live in the WaveformVisualizer.ts interop module; this component is a thin
+   bridge that feeds it datum + playback + zoom + theme. Deliberately NOT the player-bar peak-bar idiom. *@
+
+<div class="mix-waveform-bg">
+    <canvas @ref="_canvas" class="mix-waveform-canvas"></canvas>
+</div>
+
+@* The viewing controls (resolution + the three Wave 2 controls) live in WaveformVisualizerControls,
+   rendered in the mix-detail foreground row below the back button — NOT here. This component is now a
+   pure backdrop bridge; it pushes uniforms in response to the shared WaveformVisualizerControlState. *@