Accessibility: ARIA labels, keyboard nav, and tooltips

[samkeen]

Summary

Improve accessibility for screen readers and keyboard navigation.

Tasks

• Convert clickable divs to buttons in activity-timeline (line ~68)
• Add ARIA labels to expandable sections (▼▶ arrows in session-tabs)
• Add tooltips for truncated content:
  • Session IDs truncated to 8 characters
  • File paths that overflow
• Review color contrast for WCAG AA compliance:
  • text-zinc-600 dark:text-zinc-500 may be weak
• Add proper focus states to interactive elements

Files to update

• components/activity-timeline.tsx
• components/session-tabs.tsx
• app/page.tsx