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>