Fix sidebar, shortlist, palette, and compare view issues (litmus-4tgw)
Five fixes:
- Browse Themes sidebar link active on detail pages (should not be)
- Shortlist at max 5: should evict oldest instead of refusing
- Compare page: removing from shortlist should refresh; clearing should go to themes
- Detail page color palette always expanded
- Compare page: replace ColorDiffTable with per-theme color palettes at end
Summary of Changes
- Browse Themes active state: Changed to only highlight on ThemeList, not ThemeDetail
- Shortlist evicts oldest at max: Both ShortlistCheckbox and keyboard handler now remove the oldest entry when adding a 6th theme
- Compare page reacts to shortlist changes: Remove button rebuilds compare URL and navigates; clear button navigates to themes list
- Detail page palette always expanded: Changed initial state from false to true
- Compare page palette: Removed ColorDiffTable component and CSS, added per-theme color palettes at the end of the compare view
- Cleanup: Removed dead ColorDiffTable component, ANSI_NAMES constant in components.rs, and all color-diff CSS