fix(ui): wrap agent selector buttons instead of clipping overflow

[ASRagab]

Summary

• Agent buttons in the New Task dialog were rendered in a single non-wrapping flex row with flex: 1, causing buttons to shrink and clip when many agents are configured (e.g., 6+ custom agents)
• Buttons now wrap onto multiple lines with content-based sizing (flex: 0 1 auto, min-width: 70px)
• Dialog widens from 420px to 540px when more than 8 agents are present to avoid excessive rows

Before / After

Test plan

• Open New Task dialog with default agents (3-5) — buttons should display on a single row as before
• Add custom agents until 6+ are visible — buttons should wrap to a second row
• Add 9+ agents — dialog should widen to 540px
• Verify buttons with short names ("CC") don't collapse below 70px
• Verify buttons with long names render without truncation

🤖 Generated with Claude Code

[johannesjo]

Thank you very much! <3