Rework outline / table of contents

[mejo-]

📝 Summary

See https://github.com/nextcloud/text/issues/7741#issuecomment-3607495936

• Resolves: #3586
• Resolves: #5379
• Resolves: #6876
• Resolves: #7228
• Resolves: #7522
• Resolves: nextcloud/collectives#1624
• Resolves: nextcloud/collectives#1715
• Resolves: nextcloud/collectives#1777

Screenshots

Outline	Table of contents

Screencast

https://github.com/user-attachments/assets/15ba438c-569a-4b49-8e66-889d92554ed7

🚧 TODO

• [x] Outline not displayed in view mode in Collectives
• [x] RichWorkspace: Hide outline action in headings menu
• [x] Update headings only when a heading changed
• [x] Update headings also in MarkdownContentEditor
• [ ] Fix and extend tests
• [ ] Test manually in a lot of scenarios:
  • [ ] text standalone, collectives, (embedded?)
  • [ ] collectives landing page with widgets above
  • [ ] wide screen desktop, narrow screen desktop, mobile
  • [ ] full width view and not
  • [ ] sidebar open and not
  • [ ] public share
  • [ ] print view
  • [ ] long headings
  • [ ] long heading list (vertical scroll)
  • [ ] conflict handling view
  • [ ] read-only files

🏁 Checklist

• [ ] Code is properly formatted (npm run lint / npm run stylelint / composer run cs:check)
• [ ] Sign-off message is added to all commits
• [ ] Tests (unit, integration and/or end-to-end) passing and the changes are covered with tests
• [ ] Documentation (README or documentation) has been updated or is not required