fix(theater): replace max-height collapse with grid-rows + visibility; fix keyboard-focus leak when collapsed

DeepDrftPublic.Client/Controls/AudioPlayerBar/AudioPlayerBar.razor

@@ -20,7 +20,9 @@ else
                 {
                     var nowShowing = VisualizerControlState.TheaterMode;
                     <div class="dd-theater-collapsible @(nowShowing ? null : "dd-theater-collapsed")">
+                        <div class="dd-theater-collapsible-inner">
                         <NowShowingPanel Release="CurrentTrack.Release" />
+                        </div>
                     </div>
                 }
 

DeepDrftPublic.Client/Pages/CutDetail.razor

@@ -75,6 +75,7 @@ else
                a collapsing wrapper so it does not pop — IsContentHidden collapses it to zero height when
                Theater is on AND this Cut is the playing release. OFF eases it back to its normal layout. *@
             <div class="dd-theater-collapsible @(IsContentHidden ? "dd-theater-collapsed" : null)">
+            <div class="dd-theater-collapsible-inner">
             @* Header split: meta + Play/Share on the LEFT, bordered cover on the RIGHT (spec §3.1). *@
             <div class="cut-detail-header">
                 <div class="cut-detail-meta">
@@ -134,10 +135,12 @@ else
                 </div>
             </div>
             </div>
+            </div>
         </Header>
         <BodyContent>
             @* Theater Mode (Wave 2 §2): eased collapse, mirroring the Header region. *@
             <div class="dd-theater-collapsible @(IsContentHidden ? "dd-theater-collapsed" : null)">
+            <div class="dd-theater-collapsible-inner">
             @* Blurb sits between the header and the track-list divider. *@
             <ReleaseDescription Description="@release.Description" />
             <MudDivider Class="cut-detail-divider" />
@@ -169,6 +172,7 @@ else
                 </div>
             }
             </div>
+            </div>
         </BodyContent>
     </ReleaseDetailScaffold>
     </div>

DeepDrftPublic.Client/Pages/MixDetail.razor

@@ -75,6 +75,7 @@ else
                    a collapsing wrapper so it does not pop — collapsed to zero height when Theater is on AND
                    this Mix is the playing release. OFF eases the full-bleed visualizer back behind the hero. *@
                 <div class="dd-theater-collapsible @(IsContentHidden ? "dd-theater-collapsed" : null)">
+                <div class="dd-theater-collapsible-inner">
                 @* Cover-as-background hero with all metadata overlaid, square `mix-hero` sizing. The
                    cover art IS the background, so no separate cover thumbnail (CoverThumbKey defaults
                    to null). Share and play ride in as slots, matching Sessions. *@
@@ -99,12 +100,15 @@ else
                     </PlayContent>
                 </ReleaseHeroOverlay>
                 </div>
+                </div>
             </Hero>
             <BodyContent>
                 @* Theater Mode (Wave 2 §2): eased collapse, mirroring the Hero region. *@
                 <div class="dd-theater-collapsible @(IsContentHidden ? "dd-theater-collapsed" : null)">
+                    <div class="dd-theater-collapsible-inner">
                     @* Blurb sits below the hero, inside the scaffold's foreground stacking context. *@
                     <ReleaseDescription Description="@release.Description" />
+                    </div>
                 </div>
             </BodyContent>
         </ReleaseDetailScaffold>

DeepDrftPublic.Client/Pages/SessionDetail.razor

@@ -72,6 +72,7 @@ else
            collapsing wrapper so they do not pop — collapsed to zero height when Theater is on AND this
            Session is the playing release. The top row above stays. OFF eases this region back in. *@
         <div class="dd-theater-collapsible @(IsContentHidden ? "dd-theater-collapsed" : null)">
+        <div class="dd-theater-collapsible-inner">
         @* The overlay shows the cover thumbnail only when it differs from the resolved hero image —
            when there is no dedicated hero, heroImage already falls back to release.ImagePath, so the
            thumb would duplicate the background. That logic lives in ReleaseHeroOverlay. *@
@@ -98,6 +99,7 @@ else
 
         <ReleaseDescription Description="@release.Description" />
         </div>
+        </div>
 
     </MudContainer>
 }

DeepDrftPublic/wwwroot/styles/deepdrft-styles.css

@@ -370,21 +370,44 @@ h2, h3, h4, h5, h6,
 }
 
 /* Eased content collapse for Theater Mode (Phase 20 Wave 2 §2). The detail content stays mounted and
-   collapses to zero height (and fades) when .dd-theater-collapsed is applied, so toggling Theater eases
+   collapses smoothly when .dd-theater-collapsed is applied, so toggling Theater eases both directions
-   both directions instead of popping — when collapsed the content is fully out of the way and the
+   instead of popping — when collapsed the content is fully out of the way and the visualizer is
-   visualizer is unobstructed. overflow:hidden clips the content during the transition; the large open
+   unobstructed. The same pattern drives the player-bar "now showing" band so the bar grows/shrinks
-   max-height accommodates any realistic content height (it is a ceiling, not a fixed size). The same
+   smoothly too.
-   pattern drives the player-bar "now showing" band so the bar grows/shrinks smoothly too. */
+
+   Technique: grid-template-rows 1fr → 0fr interpolates the REAL content height (no 400vh ceiling
+   artifact / delayed-start that the old max-height approach had). The direct child receives
+   overflow:hidden + min-height:0 so it actually clips during the transition (the grid child is the
+   collapsing unit). visibility:hidden removes all descendants from the tab order and from pointer/
+   keyboard interaction once collapsed — this fixes the Major accessibility defect where Tab could
+   reach hidden controls. transition-behavior:allow-discrete makes visibility flip discretely: it
+   flips to hidden AFTER the ease-out finishes (so the animation plays fully), and flips back to
+   visible BEFORE the ease-in starts (so content is immediately interactive on the way back in).
+   The visibility transition is listed as 0s so it is instant when it fires; the allow-discrete
+   behaviour determines which end of the transition that instant flip occurs on. */
 .dd-theater-collapsible {
-    overflow: hidden;
+    display: grid;
-    max-height: 400vh;
+    grid-template-rows: 1fr;
     opacity: 1;
-    transition: max-height 0.45s ease, opacity 0.3s ease;
+    visibility: visible;
+    transition: grid-template-rows 0.45s ease, opacity 0.3s ease, visibility 0s;
+    transition-behavior: allow-discrete;
+}
+
+/* The single direct child clips itself during the grid-row collapse. min-height:0 overrides the
+   implicit min-height:auto that would prevent the row from shrinking past the content's intrinsic
+   height. overflow:hidden clips painted content when the row is partially collapsed. */
+.dd-theater-collapsible > * {
+    overflow: hidden;
+    min-height: 0;
 }
 
 .dd-theater-collapsed {
-    max-height: 0;
+    grid-template-rows: 0fr;
     opacity: 0;
+    /* visibility flips to hidden instantly, but allow-discrete defers it to AFTER the ease-out
+       completes (at the end of the 0.45s transition), so the animation still plays in full. */
+    visibility: hidden;
 }
 
 /* Honor reduced-motion: collapse still happens (it is layout, not decoration) but instantly, matching