## Why
Extension UI trees previously accepted only named terminal colors and literal RGB values. Semantic colors let extension content follow the active syntax theme and terminal color capabilities.
## What changed
- Accept `primary`, `surface`, `accent`, and `status-*` color roles for text foregrounds and row backgrounds.
- Resolve semantic colors against the active theme when rendering extension footer content. Prefer the `codex.accent` scope for `accent`, falling back to the theme's accent setting.
- Reuse status-line scope mappings and fallback colors, with terminal-default fallbacks for unavailable primary, surface, and accent colors.
## Testing
Add color serialization coverage and rendering snapshots for dark, light, and empty themes in truecolor and ANSI 16-color terminals, including nested foreground and background styles.
GitOrigin-RevId: 156f137859d74178f9ae6aa46a02eecb815e9802
Joe Savona
2157f98648