UX Cleanup: Simplify and declutter the app experience

[atlas-agent-omi]

Umbrella issue for UX cleanup across the app. Goal: reduce cognitive load, hide advanced features by default, and make the core experience cleaner.

Sub-issues

• UX: Remove tasks and goals from home screen (hide by default) #6324
• UX: Remove personas option from apps page and settings #6325
• UX: Simplify tasks page and improve option explanations #6326
• UX: Simplify offline sync terminology #6327
• UX: Clarify conversation templates vs prompt apps distinction #6328
• UX: Cleanup app creation flow — gate technical details #6329