* chore: update deps, fix escape codes, expand tests, add README
- Bump Go 1.18 → 1.26, simplecolorpalettes v0.9.5 → v0.9.7
- Fix swapped fg/bg ANSI escape code values in trueColorString
- Expand test suite from 2 to 13 tests (determinism, positivity, color assignment, background contrast, stringer palette)
- Add README with usage examples
* feat: add OKLCH-aware palette generation
Add GenerateOKLCHPalette() which creates n evenly-spaced colors in the
OKLCH color space at a given lightness and chroma. This produces
perceptually uniform palettes where all colors appear equally bright.
Uses the new OKLCH support from simplecolorpalettes.
Note: go.mod contains a replace directive for local development that
must be removed before merge (after simplecolorpalettes is published).
* build: update simplecolorpalettes to v0.9.8 (charmtone palette)
