fix(player): 评论输入改为透明浮层并消除收起键盘抖动

test/comment/drama_comments_sheet_test.dart

@@ -352,10 +352,18 @@ void main() {
     final composer = find.byKey(const Key('comment-composer-sheet'));
     final composerInput = find.byKey(const Key('comment-composer-input'));
     expect(composer, findsOneWidget);
-    expect(
-      ModalRoute.of(tester.element(composer))?.barrierColor,
-      Colors.transparent,
-    );
+    final overlayRoot = find.byKey(const Key('comment-composer-overlay'));
+    expect(overlayRoot, findsOneWidget);
+    final overlayStack = tester.widget<Stack>(overlayRoot);
+    expect(overlayStack.children, hasLength(2));
+    final dismissLayer = overlayStack.children.first as Positioned;
+    expect(dismissLayer.left, 0);
+    expect(dismissLayer.top, 0);
+    expect(dismissLayer.right, 0);
+    expect(dismissLayer.bottom, 0);
+    final dismissGesture = dismissLayer.child as GestureDetector;
+    expect(dismissGesture.child, isNull);
+    expect(dismissGesture.behavior, HitTestBehavior.opaque);
     final compactHeight = tester.getSize(composer).height;
     expect(compactHeight, inInclusiveRange(100, 150));
     expect(tester.widget<TextField>(composerInput).focusNode?.hasFocus, isTrue);
@@ -486,6 +494,33 @@ void main() {
     expect(sheet, findsNothing);
   });
 
+  testWidgets(
+    'should_close_composer_overlay_on_back_without_closing_comments',
+    (tester) async {
+      final repository = FakeCommentRepository(
+        pages: [
+          CommentPage(
+            comments: [commentFixture(id: '10', content: 'A comment')],
+          ),
+        ],
+      );
+
+      await _pumpSheet(tester, repository: repository);
+      await tester.tap(find.byKey(const Key('comment-input-placeholder')));
+      await tester.pumpAndSettle();
+
+      final sheet = find.byKey(const Key('player-comments-sheet'));
+      final composer = find.byKey(const Key('comment-composer-sheet'));
+      expect(sheet, findsOneWidget);
+      expect(composer, findsOneWidget);
+
+      await tester.binding.handlePopRoute();
+      await tester.pumpAndSettle();
+      expect(sheet, findsOneWidget);
+      expect(composer, findsNothing);
+    },
+  );
+
   testWidgets('should_use_polished_comment_sizes', (tester) async {
     final repository = FakeCommentRepository(
       pages: [