fix(player): 评论入口改为假输入框点击唤起

test/widget_test.dart

@@ -248,6 +248,8 @@ void main() {
     await tester.tap(find.byKey(const Key('player-rail-comments')));
     await tester.pumpAndSettle();
     expect(find.text('No comments yet.'), findsOneWidget);
+    await tester.tap(find.byKey(const Key('comment-input-placeholder')));
+    await tester.pumpAndSettle();
     await tester.enterText(find.byKey(const Key('comment-input')), 'Nice demo');
     await tester.pump();
     await tester.tap(find.byKey(const Key('comment-post')));