fix: align collaboration mode overrides

[Dimillian]

Summary

• parse collaboration modes with the new struct shape (mode + settings)
• show Code label in the collaboration mode dropdown
• reflect collaboration-mode model/effort in composer via helper hook (applies to any selected mode)
• render single-line code blocks without the full header/copy wrapper (URL lines become link blocks)

Notes

• composer model/effort selectors remain disabled while a mode is selected
• clearing the mode restores previous selections

Testing

• npm run lint
• npm run test
• npm run typecheck