Adds a configurable font size option for the webchat interface.
Changes:
- Add chatFontSize setting to UiSettings (small/medium/large/x-large)
- Add --font-size-chat CSS variable in base.css
- Update chat text styles to use the CSS variable
- Add applyChatFontSize function to apply setting to document
- Add font size dropdown control in chat controls UI
- Add styles for the font size control
Resolves#3027
- Replace orange accent (#f59f4a) with signature red (#ff4d4d)
- Switch from IBM Plex/Unbounded/Work Sans to Inter/JetBrains Mono
- Replace emoji icons with Lucide-style SVG icons throughout
- Add comprehensive CSS design tokens (colors, borders, semantic states)
- Update tool-display.json to use icon names instead of emoji
- Rebuild control-ui dist bundle