- Redesign Button rendering with half-block caps (U+2590/U+258C) and accent-tinted background
- Apply matching cap style and background to TextField and SecureField
- Add foregroundQuaternary to Palette for subtle UI elements like spinner tracks
- Fix border saturation in all palette presets to preserve hue instead of going gray
- Rework Spinner bouncing trail to interpolate from highlight to quaternary via Color.lerp
- Fix Spinner label to use palette foreground color
- Fix FrameDiffWriter to use ESC[2K for reliable line clearing
- Add Layoutable conformance to NavigationSplitView for height-flexible layout
- Update tests for new button cap style
phranck