Desktop: video freeze recovery, session fixes, Home redesign

- Player + VideoController per session; Reload video (Ctrl+R) and a
  frozen-picture watchdog that reloads automatically.
- Shortcuts no longer fire while typing; empty swap disabled;
  hwdec setting/env actually applied.
- Idle unready measured from real inactivity; cancellable reconnects
  and setup; ready restored from server state; kicked/failed host
  stops its server; graceful leave on window close; no URLs with
  keys in display names.
- Welcome + connect screens replaced by one Home screen with Join and
  Host cards, recent servers, Settings, Integrations and About.

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

apps/desktop/test/frame_watchdog_test.dart

@@ -0,0 +1,108 @@
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:watch_together/src/playback/frame_watchdog.dart';
+
+final _t0 = DateTime.utc(2026, 1, 1);
+
+/// Feeds one sample per second; [frames]/[pos] give the value at second i.
+List<bool> _run(
+  FrameWatchdog w,
+  int seconds, {
+  required int? Function(int i) frames,
+  double Function(int i)? pos,
+  bool Function(int i)? eligible,
+  int start = 0,
+}) {
+  return [
+    for (var i = start; i < start + seconds; i++)
+      w.feed(FrameSample(
+        at: _t0.add(Duration(seconds: i)),
+        position: pos?.call(i) ?? i.toDouble(),
+        frames: frames(i),
+        eligible: eligible?.call(i) ?? true,
+      )),
+  ];
+}
+
+void main() {
+  test('hashes tell frames apart and ignore the edges', () {
+    final a = ByteData(100 * 60 * 4);
+    final b = ByteData(100 * 60 * 4);
+    expect(hashCenterPixels(a, 100, 60), hashCenterPixels(b, 100, 60));
+    b.setUint8((2 * 100 + 2) * 4, 255); // corner: overlay area
+    expect(hashCenterPixels(a, 100, 60), hashCenterPixels(b, 100, 60));
+    b.setUint8((30 * 100 + 50) * 4, 255); // centre: video
+    expect(hashCenterPixels(a, 100, 60), isNot(hashCenterPixels(b, 100, 60)));
+    final raw = Uint8List(1 << 20);
+    final h = hashSpread(raw);
+    raw[raw.length ~/ 2 - (raw.length ~/ 2) % (raw.length ~/ 4096)] = 1;
+    expect(hashSpread(raw), isNot(h));
+  });
+
+  test('frames advancing never fires', () {
+    final w = FrameWatchdog();
+    expect(_run(w, 30, frames: (i) => i * 30), everyElement(isFalse));
+  });
+
+  test('frames stuck while position advances fires once after ~3 s', () {
+    final w = FrameWatchdog();
+    final fired = _run(w, 20, frames: (i) => i < 5 ? i * 30 : 150);
+    expect(fired.where((f) => f).length, 1);
+    expect(fired.indexOf(true), 8, reason: 'stuck from t=5, 3 s later');
+  });
+
+  test('pause, buffering, missing data and seeks do not fire', () {
+    final w = FrameWatchdog();
+    // Paused / buffering: not eligible.
+    expect(_run(w, 10, frames: (_) => 100, eligible: (_) => false),
+        everyElement(isFalse));
+    // No video output (headless / audio-only).
+    expect(_run(w, 10, frames: (_) => null, start: 10), everyElement(isFalse));
+    // Position stuck too (network stall): not a frozen picture.
+    expect(_run(w, 10, frames: (_) => 100, pos: (_) => 50, start: 20),
+        everyElement(isFalse));
+    // Seeking every 2 s with frames stuck in between: jumps reset it.
+    expect(
+        _run(w, 12,
+            frames: (_) => 100,
+            pos: (i) => i.isEven ? i * 10.0 : i * 10.0 - 9,
+            start: 30),
+        everyElement(isFalse));
+  });
+
+  test('no reload loop: re-arms only after 10 s of healthy frames', () {
+    final w = FrameWatchdog();
+    expect(_run(w, 10, frames: (_) => 7).where((f) => f).length, 1);
+    w.reset(); // new player
+    // Brief healthy spell, then stuck again: must not fire.
+    expect(
+        _run(w, 15, frames: (i) => i < 13 ? i : 13, start: 10)
+            .where((f) => f)
+            .length,
+        0);
+    // Healthy for 10 s+, then stuck: fires again.
+    w.reset();
+    expect(
+        _run(w, 25, frames: (i) => i < 42 ? i : 42, start: 30)
+            .where((f) => f)
+            .length,
+        1);
+  });
+
+  test('still scene: dismiss re-arms after another full stall', () {
+    final w = FrameWatchdog();
+    final fired = <int>[];
+    for (var i = 0; i < 20; i++) {
+      if (w.feed(FrameSample(
+          at: _t0.add(Duration(seconds: i)),
+          position: i.toDouble(),
+          frames: 5,
+          eligible: true))) {
+        fired.add(i);
+        w.dismiss();
+      }
+    }
+    expect(fired, [3, 6, 9, 12, 15, 18]);
+  });
+}