docs: 更新 CLAUDE.md 添加代码风格和随机播放逻辑说明

- 添加项目使用 Tab 缩进的说明
- 添加随机播放模式的详细逻辑说明
- 说明 shuffleList 和 currentIndex 的关系

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

CLAUDE.md

@@ -83,6 +83,12 @@ npm run qc                 # Alias for quality-check
 - **URL Refresh Logic**: Checks resource availability before playback/preload
 - **Cache Invalidation**: Automatic cleanup when resource URLs change
 
+### Shuffle/Random Play Logic
+- **shuffleList**: Array storing the shuffled order of original list indices
+- **currentIndex**: In shuffle mode, this is the index within shuffleList
+- **Accessing current song**: `list[shuffleList[currentIndex]]` in shuffle mode
+- **getNextIndex**: Returns the actual list index of the next song to play
+
 ## File Structure Notes
 
 ### `/src/utils/`
@@ -99,6 +105,13 @@ npm run qc                 # Alias for quality-check
 - **content.js**: Injects the Vue app into target websites
 - **background.js**: Extension background script
 
+## Code Style and Formatting
+
+### Indentation
+- **This project uses Tab indentation (not spaces)**
+- Ensure all code edits maintain consistent Tab indentation
+- When editing files, preserve the existing Tab character formatting
+
 ## Development Considerations
 
 ### Extension Context