fix: keep the DVD player whole

Removing gtk-layer-shell from the dependencies broke classroom-dvd on the
first run, and deleting the dock's stylesheet took the DVD control bar's
styling with it. Both go back: the template under a name that says what
still uses it, and the dependency with a line in the package description
explaining that it is there for the disc player and not for a dock.

A probe overlay confirms gtk-layer-shell works under KWin, so the loading
cover survives the move. The focus helper still speaks sway, which is
written down rather than papered over.

Co-Authored-By: Claude Opus 5 <[email protected]>

tools/build-release.sh

@@ -331,6 +331,10 @@ install -Dm644 \
     "$ROOT/config/icons/dvd.svg" \
     "$STAGE/etc/ekklesia-classroom/icons/dvd.svg"
 
+install -Dm644 \
+    "$ROOT/config/overlay/style.css.in" \
+    "$STAGE/etc/ekklesia-classroom/overlay/style.css.in"
+
 # DVD mode control bar.
 for icon in media-play media-pause chapter-prev chapter-next \
         disc-menu eject close; do