feat(theme): add color0-color255 syntax and fix 256-color palette, Fi…

[Samyra312007]

Fixes: #2081

Summary

Add color0 to color255 syntax support for addressing all 256 terminal colors by number, and fix the 256-color palette to match the actual xterm specification.

Changes

src/config/color.c

• Fixed color values: Replaced all 256 HSL values in the color_names[] array with correct values derived from the standard xterm 256-color palette:

  • Colors 0–15: Standard ANSI defaults (e.g., red was hsl(0,100%,25%) = #800000, now hsl(0,100%,40%) = #CD0000)
  • Colors 16–231: 6×6×6 color cube computed from rgb({0,95,135,175,215,255})
  • Colors 232–255: 24-step grayscale ramp (rgb(8,8,8) to rgb(238,238,238))
  • Key fix: gold1 (index 220) was hsl(0,100%,50%) = pure red, now hsl(51,100%,50%) = correct gold

• Added colorN syntax: Enhanced find_col() to parse color0 through color255 (case-insensitive), returning the numeric index directly. This solves the "fewer than 256 accessible colors" problem caused by duplicate names (e.g., blue3 at indices 19 and 20).

src/ui/console.c

• Updated /theme colours: Replaced outdated help text with clear instructions on using color0 to color255 and the standard xterm colour names.

Backward Compatibility

• All existing named colors are preserved unchanged
• All existing .theme files continue to work without modification
• The colorN syntax is purely additive

How to test the functionality

1. Build with your usual flags: meson setup build_run -Dtests=true && meson compile -C build_run
2. Run the tests: meson test -C build_run
3. Launch profanity and run /theme colours — verify the updated help text appears
4. Load a theme that uses numeric syntax, e.g. add this to a .theme file:

   [colours]
   titlebar=color21
   titlebar.text=color255

5. Verify the colors render correctly
6. Verify existing themes (e.g. themes/original) still work with named colors like gold1, navyblue, etc.