feat(mix-visualizer): Phase 10 tuning — smooth waveform, bouncy collision, 8 knobs

Smooth the loudness contour (~50 ms envelope at preprocessing + decode-time, plus
smootherstep render reconstruction); retune wax↔waveform collision to bouncy/sub-unity
(no explosion/stuck/jitter); split the bubbles knob into fluid-amount + fluid-viscosity
(cohesion via uniform-only smin/wobble); retune scroll/gravity/heat/width ranges; make
the colour rotation visible and boost OKLab chroma; the controls bar now holds its
layout and hides only its knobs via a Visible parameter.

DeepDrftPublic.Client/Pages/MixDetail.razor

@@ -53,15 +53,13 @@ else
                                ShowMeta="false"
                                ShowShareRow="false">
             <TopContent>
-                @* The seven-knob band lives in its own full-width area below the back/lamp top row.
-                   Blazor — not CSS — controls its visibility: it is rendered only while the lava-lamp is
-                   on, so when off it is not in the DOM at all. No background, no animation, no reflow of
-                   the row above. The band mutates the shared MixVisualizerControlState; the backdrop
-                   bridge pushes the dials. A knob drag does not toggle it — the lamp's click does. *@
-                @if (_controlsExpanded)
-                {
-                    <MixVisualizerControls />
-                }
+                @* The eight-knob band lives in its own full-width area below the back/lamp top row.
+                   Phase 10 §4: the control is ALWAYS rendered; the lava-lamp toggle feeds its Visible
+                   parameter, and the control itself @if-gates the knobs while holding the container's
+                   reserved height — so content below never pops on toggle. The band mutates the shared
+                   MixVisualizerControlState; the backdrop bridge pushes the dials. A knob drag does not
+                   toggle it — the lamp's click does. *@
+                <MixVisualizerControls Visible="@_controlsExpanded" />
             </TopContent>
             <TopRightAction>
                 @* Lava-lamp button top-right, across from the back link. Toggles the knob band below the