- Add deriveExportColors() to compute page/card/info backgrounds from userMessageBg
- Use luminance detection to adapt colors for light/dark themes
- Use info-bg for model-change, compaction, system-prompt sections
- Use selectedBg for hover states and summary backgrounds
- Add scroll-to-message with highlight when clicking tree nodes
- Fix mobile overlay to close sidebar on click
- Wider sidebar (400px) with search and filter controls
f53cabe1e3