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

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>
 }