* feat: Add Web Viewer bridge for referencing open web tabs in chat.
* refactor: Simplify markdown image extraction parser。
* fix: Prevent web selection from auto-reappearing after removal or new chat.
* fix: Suppress active web tab when web selection exists.
* feat: Add YouTube transcript extraction for Web Viewer tabs.
* feat: Built-in slash prompts for web clippers.
* feat: Improve web selection tracking and simplify context settings
- Merge context settings: combine note/web active content and selection settings
- Add auto-clear for web selection badge when deselected on page
- Make note and web selections mutually exclusive
- Show website favicon in web selection badge
- Add migration logic and tests for settings
