feat: Replace task item icons with clearer state indicators

[charlesvien]

Problem

The sidebar task icons conflated workspace mode (local/worktree) with task state, and the ArrowsSplit worktree icon read as a share icon at small sizes.

Changes

1. Replace BellRinging with HandPalm for permission-needed state
2. Replace Laptop/ArrowsSplit default icons with ChatCircle
3. Replace unread ■ square with filled Circle dot
4. Promote needsPermission to highest priority in the icon chain
5. Remove worktree-specific icons and useFocusStore dependency

How did you test this?

Manually

[charlesvien]

• feat: Replace task item icons with clearer state indicators #1613 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.