Add troubleshooting notes for restricted pages and failed captures

[Najariya]

Goal

Help users understand why some pages cannot be captured and what to do when capture fails.

Cover

• chrome:// and browser internal pages
• Chrome Web Store pages
• file:// local files
• very long or dynamic pages
• missing permissions or extension reload needs

Done when

• README or docs/STATUS.md links to a troubleshooting section
• Error cases use privacy-safe language and do not overpromise browser-restricted behavior