Protocol 10 presence gate, drop/paste anywhere, quick UI fixes

Ready gate: whoever is in the server while it is not playing counts (joining
while playing does not pause anyone); a swap counts everyone present and
keeps ready flags; the quorum rule is gone. Optional 'Unready when the
video changes'. No 'Skip 1:30' guess when the media has chapters.

Drag & drop and Ctrl+V anywhere (fox_utils): files, folders and links get a
small card asking how to open them. Files series start collapsed.

UI: Tab never moves focus and Space is always ready outside text fields;
chat focuses its field; unread badge on uosc and a chip in fullscreen;
people-only chat with an Activity toggle; skip pills show 5 s then with
the controls; volume up to 150%; own avatar same size as the party.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/lib/src/shell/player_status.dart

@@ -193,7 +193,7 @@ class _PlayerStatusState extends State<PlayerStatus> {
                   child: GestureDetector(
                     key: const ValueKey('player-status'),
                     onTap: ready ? coord.toggleReady : null,
-                    child: _Glass(
+                    child: PlayerGlass(
                       child: AnimatedSize(
                         duration: easeTime,
                         curve: ease,
@@ -217,9 +217,10 @@ class _PlayerStatusState extends State<PlayerStatus> {
   }
 }
 
-class _Glass extends StatelessWidget {
+/// Frosted dark glass in a pill: the status pill, the unread chip.
+class PlayerGlass extends StatelessWidget {
   final Widget child;
-  const _Glass({required this.child});
+  const PlayerGlass({super.key, required this.child});
 
   @override
   Widget build(BuildContext context) {