1.0 shell: one window with a party strip; protocol 9 profile + avatars by hash

The shell (lib/src/shell/) replaces the Home and session screens:
- Party strip: profile, Library / Schedule / Settings tabs, Join and
  Host cards (hosting no longer takes media), status-ring avatar stack
  with the member list, chat & activity panel, Leave.
- The real session player is mounted once and shown full, as a
  draggable corner-snapping mini player, or fullscreen (window_manager,
  party and toasts overlaid); the Video is never mounted twice.
- Profile popover with inline rename, colour and a crop picker (256 px
  PNG), pushed live to the session; avatar toasts; waiting pill.
- Motion kit (fastEaseInToSlowEaseOut, fade-through, popovers,
  mouse-drag/wheel horizontal scrolling).
- Library = the existing picker for now (restyled next round); Schedule
  = the new SchedulePage; Settings = left nav over the existing panels.

Protocol 9 (packages/core, packages/server, sync client):
- {"t":"profile"} renames / changes the picture mid-session ("rename",
  "avatar" feed actions); names are cleaned the same way at hello.
- state.members carry avatarHash; pictures are served once from
  /a/<sid>/<token>/<hash> (PNG/JPEG/WebP/GIF by magic bytes only) and
  cached by hash in the app (AvatarCache).

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

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

@@ -0,0 +1,228 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:signals/signals_flutter.dart';
+import 'package:sync_relay_core/core.dart' show MemberView;
+
+import '../session/session_coordinator.dart' show ToastItem;
+import '../state/session_state.dart';
+import 'avatar.dart';
+import 'motion.dart';
+
+/// One toast on screen: who (null = the app itself), what, and whether it
+/// is on its way out.
+class ShellToast {
+  final int id;
+  final AvatarInfo? who;
+  final IconData? icon;
+  final String text;
+  final bool chat;
+  bool leaving = false;
+  ShellToast({required this.id, required this.text, this.who, this.icon, this.chat = false});
+}
+
+/// Splits a coordinator toast into who and what: feed toasts start with
+/// the actor's name ("Bob joined", "Bob: hi"); anything else is the app's.
+ShellToast shellToastFor(ToastItem t, Iterable<String> names, AvatarInfo Function(String name) avatar) {
+  final sorted = names.where((n) => n.isNotEmpty).toSet().toList()..sort((a, b) => b.length - a.length);
+  for (final n in sorted) {
+    if (t.text.startsWith('$n: ')) {
+      return ShellToast(id: t.id, who: avatar(n), text: t.text.substring(n.length + 2), chat: true);
+    }
+    if (t.text.startsWith('$n ')) {
+      final rest = t.text.substring(n.length + 1);
+      final icon = rest.startsWith('joined')
+          ? Icons.login
+          : rest.startsWith('left')
+              ? Icons.logout
+              : rest.startsWith('kicked')
+                  ? Icons.gavel
+                  : rest.startsWith('changed')
+                      ? Icons.swap_horiz
+                      : Icons.info_outline;
+      return ShellToast(id: t.id, who: avatar(n), text: rest, icon: icon);
+    }
+  }
+  return ShellToast(id: t.id, text: t.text, icon: Icons.info_outline);
+}
+
+/// The coordinator's toasts as cards with avatars, bottom-left: each
+/// slides in, stays [life], then slides out and collapses its gap.
+class PartyToasts extends StatefulWidget {
+  final Duration life;
+  const PartyToasts({super.key, this.life = const Duration(seconds: 5)});
+
+  @override
+  State<PartyToasts> createState() => _PartyToastsState();
+}
+
+class _PartyToastsState extends State<PartyToasts> {
+  final _shown = <ShellToast>[];
+  final _timers = <Timer>[];
+  Set<int> _seen = {};
+  late final void Function() _stop;
+
+  @override
+  void initState() {
+    super.initState();
+    final coord = SessionState.instance.coordinator;
+    // What was there before this mounted is old news.
+    _seen = {for (final t in coord.toasts.peek()) t.id};
+    _stop = effect(() {
+      final items = coord.toasts.value;
+      final fresh = [for (final t in items) if (!_seen.contains(t.id)) t];
+      _seen = {for (final t in items) t.id};
+      if (fresh.isEmpty) return;
+      // Only new toasts re-run this, not the party they mention.
+      untracked(() {
+        final r = coord.serverState.value;
+        final names = [
+          for (final m in r?.members ?? const <MemberView>[]) m.name,
+          for (final f in coord.feedLog.value) f.actor,
+        ];
+        for (final t in fresh) {
+          _add(shellToastFor(t, names, (n) => avatarForName(n, coord)));
+        }
+      });
+    });
+  }
+
+  void _add(ShellToast t) {
+    // Not from inside the effect's build-time notification.
+    scheduleMicrotask(() {
+      if (!mounted) return;
+      setState(() => _shown.add(t));
+      _timers.add(Timer(widget.life, () {
+        if (mounted) setState(() => t.leaving = true);
+      }));
+      _timers.add(Timer(widget.life + easeTime, () {
+        if (mounted) setState(() => _shown.remove(t));
+      }));
+    });
+  }
+
+  @override
+  void dispose() {
+    _stop();
+    for (final t in _timers) {
+      t.cancel();
+    }
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) => IgnorePointer(child: ToastColumn(toasts: _shown.reversed.take(6).toList().reversed.toList()));
+}
+
+class ToastColumn extends StatelessWidget {
+  final List<ShellToast> toasts;
+  const ToastColumn({super.key, required this.toasts});
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        for (final t in toasts)
+          TweenAnimationBuilder<double>(
+            key: ValueKey(t.id),
+            tween: Tween(begin: 0, end: 1),
+            duration: easeTime,
+            curve: ease,
+            builder: (context, v, child) => Opacity(
+              opacity: v,
+              child: Transform.translate(offset: Offset(-24 * (1 - v), 0), child: child),
+            ),
+            // Leaving: slide back out, fade, and collapse the gap it leaves.
+            child: AnimatedAlign(
+              duration: easeTime,
+              curve: ease,
+              alignment: Alignment.topLeft,
+              heightFactor: t.leaving ? 0 : 1,
+              child: AnimatedSlide(
+                duration: easeTime,
+                curve: ease,
+                offset: t.leaving ? const Offset(-0.25, 0) : Offset.zero,
+                child: AnimatedOpacity(
+                  duration: easeTime,
+                  curve: ease,
+                  opacity: t.leaving ? 0 : 1,
+                  child: Padding(padding: const EdgeInsets.only(top: 8), child: ToastCard(toast: t)),
+                ),
+              ),
+            ),
+          ),
+      ],
+    );
+  }
+}
+
+class ToastCard extends StatelessWidget {
+  final ShellToast toast;
+  const ToastCard({super.key, required this.toast});
+
+  @override
+  Widget build(BuildContext context) {
+    final scheme = Theme.of(context).colorScheme;
+    final who = toast.who;
+    return Material(
+      elevation: 8,
+      color: scheme.surfaceContainerHigh.withValues(alpha: 0.95),
+      borderRadius: BorderRadius.circular(14),
+      child: ConstrainedBox(
+        constraints: const BoxConstraints(maxWidth: 380),
+        child: Padding(
+          padding: const EdgeInsets.fromLTRB(10, 10, 16, 10),
+          child: Row(
+            mainAxisSize: MainAxisSize.min,
+            crossAxisAlignment: who == null ? CrossAxisAlignment.center : CrossAxisAlignment.start,
+            children: [
+              if (who != null)
+                StatusAvatar(info: who, size: 38, badges: false)
+              else
+                CircleAvatar(
+                  radius: 19,
+                  backgroundColor: scheme.primary.withValues(alpha: 0.15),
+                  child: Icon(toast.icon ?? Icons.info_outline, size: 18, color: scheme.primary),
+                ),
+              const SizedBox(width: 12),
+              Flexible(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    if (who != null) ...[
+                      Row(
+                        mainAxisSize: MainAxisSize.min,
+                        children: [
+                          Flexible(
+                            child: Text(who.name,
+                                maxLines: 1,
+                                overflow: TextOverflow.ellipsis,
+                                style: const TextStyle(fontWeight: FontWeight.w700, fontSize: 15)),
+                          ),
+                          if (toast.icon != null) ...[
+                            const SizedBox(width: 6),
+                            Icon(toast.icon, size: 16, color: scheme.primary),
+                          ],
+                        ],
+                      ),
+                      const SizedBox(height: 2),
+                    ],
+                    Text(
+                      toast.text,
+                      style: TextStyle(
+                        fontSize: toast.chat ? 15 : 14,
+                        color: toast.chat || who == null ? scheme.onSurface : scheme.onSurfaceVariant,
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}