video: desktop controls, shared scrubber, lifecycle guard and first-frame gate; zoomable and adapter tweaks

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

test/video/video_lifecycle_test.dart

@@ -0,0 +1,95 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:leaf_widgets/leaf_widgets.dart';
+
+void main() {
+  testWidgets('backgrounding pauses a playing child, foreground resumes it', (tester) async {
+    var pauses = 0;
+    var resumes = 0;
+    var playing = true;
+
+    await tester.pumpWidget(MaterialApp(
+      home: StatefulBuilder(
+        builder: (context, setState) => VideoLifecycleGuard(
+          isPlaying: playing,
+          onPause: () {
+            pauses++;
+            setState(() => playing = false);
+          },
+          onResume: () {
+            resumes++;
+            setState(() => playing = true);
+          },
+          child: const SizedBox.shrink(),
+        ),
+      ),
+    ));
+
+    tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.paused);
+    await tester.pump();
+    expect(pauses, 1);
+
+    tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.resumed);
+    await tester.pump();
+    expect(resumes, 1);
+  });
+
+  testWidgets('idle child gets no calls on background round-trip', (tester) async {
+    var pauses = 0;
+    var resumes = 0;
+
+    await tester.pumpWidget(MaterialApp(
+      home: VideoLifecycleGuard(
+        isPlaying: false,
+        onPause: () => pauses++,
+        onResume: () => resumes++,
+        child: const SizedBox.shrink(),
+      ),
+    ));
+
+    tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.paused);
+    await tester.pump();
+    tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.resumed);
+    await tester.pump();
+    expect(pauses, 0);
+    expect(resumes, 0);
+  });
+
+  testWidgets('covering route pauses, uncovering resumes', (tester) async {
+    var pauses = 0;
+    var resumes = 0;
+    var playing = true;
+
+    await tester.pumpWidget(MaterialApp(
+      home: StatefulBuilder(
+        builder: (context, setState) => VideoLifecycleGuard(
+          isPlaying: playing,
+          onPause: () {
+            pauses++;
+            setState(() => playing = false);
+          },
+          onResume: () {
+            resumes++;
+            setState(() => playing = true);
+          },
+          child: Builder(
+            builder: (context) => TextButton(
+              onPressed: () => showDialog(context: context, builder: (_) => const Text('cover')),
+              child: const Text('open'),
+            ),
+          ),
+        ),
+      ),
+    ));
+
+    await tester.tap(find.text('open'));
+    await tester.pumpAndSettle();
+    expect(find.text('cover'), findsOneWidget);
+    expect(pauses, 1);
+
+    Navigator.of(tester.element(find.text('cover'))).pop();
+    await tester.pumpAndSettle();
+    expect(resumes, 1);
+  });
+}