循环播放开关

功能

• 在朗读弹出条上增加循环开关，不改变原有按钮行布局
• 开关以播放/暂停键右下角的小角标形式显示：
  • 灰色：关闭
  • 蓝色：已开启循环
• 循环对本地语音和云端语音都有效
• 切换上一句/下一句后，自动循环新句子
• 暂停/恢复、切换音色、调节语速后循环状态保持
• 关闭循环时如果当前句刚好播完，会正常推进到下一句，不会卡住

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Features

• Adds a loop toggle to the Read Aloud popup without changing the layout of the existing button row
• The toggle is a small badge at the bottom-right corner of the play/pause button:
  • Gray: loop off
  • Blue: loop on
• Works with both local (system TTS) and remote (cloud TTS) voices
• After skipping to the previous or next sentence, the new sentence is looped
• Loop state is preserved across pause/resume, voice changes, and speed changes
• Turning loop off right after a sentence ends advances to the next sentence normally instead of stalling