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/controls/volume.dart

@@ -0,0 +1,146 @@
+import 'package:flutter/gestures.dart';
+import 'package:flutter/material.dart';
+import 'package:media_kit/media_kit.dart';
+
+import '../playback/playback_controller.dart' show PlaybackController;
+
+/// The player's top volume (mpv's `volume-max`): past 100 % mpv amplifies.
+const maxVolume = PlaybackController.maxVolume * 1.0;
+
+/// The part of the volume bar above 100 %.
+const boostColor = Color(0xFFFFB74D);
+
+/// [volume] moved by [delta] (wheel, keys), kept within 0..[maxVolume].
+double stepVolume(double volume, double delta) => (volume + delta).clamp(0.0, maxVolume);
+
+/// A thin volume track over 0..[maxVolume]: filled up to the volume, the
+/// part above 100 % in [boostColor], a tick at 100 %. Click or drag sets
+/// it.
+class VolumeBar extends StatelessWidget {
+  final double volume;
+  final ValueChanged<double> onChanged;
+  final double width;
+  final Color color;
+  final Color trackColor;
+  const VolumeBar({
+    super.key,
+    required this.volume,
+    required this.onChanged,
+    this.width = 64,
+    this.color = Colors.white,
+    this.trackColor = Colors.white30,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    void at(double x) => onChanged((x / width * maxVolume).clamp(0.0, maxVolume).roundToDouble());
+    return GestureDetector(
+      behavior: HitTestBehavior.opaque,
+      onTapDown: (e) => at(e.localPosition.dx),
+      onHorizontalDragUpdate: (e) => at(e.localPosition.dx),
+      child: SizedBox(
+        width: width,
+        height: 24,
+        child: CustomPaint(painter: _VolumePainter(volume.clamp(0.0, maxVolume), color, trackColor)),
+      ),
+    );
+  }
+}
+
+class _VolumePainter extends CustomPainter {
+  final double volume;
+  final Color color, trackColor;
+  _VolumePainter(this.volume, this.color, this.trackColor);
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    final y = size.height / 2;
+    double x(double v) => size.width * v / maxVolume;
+    final line = Paint()
+      ..strokeWidth = 3
+      ..strokeCap = StrokeCap.round;
+    canvas.drawLine(Offset(0, y), Offset(size.width, y), line..color = trackColor);
+    final full = x(100);
+    canvas.drawLine(Offset(full, y - 5), Offset(full, y + 5), Paint()
+      ..color = trackColor
+      ..strokeWidth = 1.5);
+    if (volume > 0) canvas.drawLine(Offset(0, y), Offset(x(volume.clamp(0, 100)), y), line..color = color);
+    if (volume > 100) canvas.drawLine(Offset(full, y), Offset(x(volume), y), line..color = boostColor);
+    canvas.drawCircle(Offset(x(volume), y), 5, Paint()..color = volume > 100 ? boostColor : color);
+  }
+
+  @override
+  bool shouldRepaint(_VolumePainter old) =>
+      old.volume != volume || old.color != color || old.trackColor != trackColor;
+}
+
+/// Volume for the standard bar (instead of media_kit's, which stops at
+/// 100): the icon mutes / unmutes, hovering shows a [VolumeBar], the
+/// wheel steps 5 %.
+class VolumeButton extends StatefulWidget {
+  final Player player;
+  final FocusNode? focusNode;
+  const VolumeButton({super.key, required this.player, this.focusNode});
+
+  @override
+  State<VolumeButton> createState() => _VolumeButtonState();
+}
+
+class _VolumeButtonState extends State<VolumeButton> {
+  bool _hover = false;
+  double _beforeMute = 100;
+
+  @override
+  Widget build(BuildContext context) {
+    final player = widget.player;
+    return StreamBuilder<double>(
+      stream: player.stream.volume,
+      initialData: player.state.volume,
+      builder: (context, snap) {
+        final v = snap.data ?? 100;
+        return MouseRegion(
+          onEnter: (_) => setState(() => _hover = true),
+          onExit: (_) => setState(() => _hover = false),
+          child: Listener(
+            onPointerSignal: (e) {
+              if (e is PointerScrollEvent && e.scrollDelta.dy != 0) {
+                player.setVolume(stepVolume(v, e.scrollDelta.dy < 0 ? 5 : -5));
+              }
+            },
+            child: Row(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                const SizedBox(width: 4),
+                IconButton(
+                  key: const ValueKey('volume-button'),
+                  focusNode: widget.focusNode,
+                  tooltip: 'Volume ${v.round()} %',
+                  iconSize: 22,
+                  color: Colors.white,
+                  onPressed: () {
+                    if (v > 0) {
+                      _beforeMute = v;
+                      player.setVolume(0);
+                    } else {
+                      player.setVolume(_beforeMute <= 0 ? 100 : _beforeMute);
+                    }
+                  },
+                  icon: Icon(v <= 0 ? Icons.volume_off : (v < 50 ? Icons.volume_down : Icons.volume_up)),
+                ),
+                AnimatedSize(
+                  duration: const Duration(milliseconds: 150),
+                  child: _hover
+                      ? Padding(
+                          padding: const EdgeInsets.only(left: 4, right: 12),
+                          child: VolumeBar(volume: v, onChanged: player.setVolume),
+                        )
+                      : const SizedBox.shrink(),
+                ),
+              ],
+            ),
+          ),
+        );
+      },
+    );
+  }
+}