feat: add OKLCH-aware palette generation (#5)

* 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)

README.md

@@ -1,17 +1,50 @@
+# colorhash
 
+Deterministic color assignment from arbitrary input. Feed it a string or byte stream and get back a consistent color every time.
 
- - Take in arbitrary input and return a deterministic color
- - Color chosen can be limited in several ways:
-   - only visually / noticibly distinct colors to choose from
-   - Color exclusions
-     - dynamic color exclusions (optional terminal context)
-   - colors within different terminal support classes (i.e. term-256)
+## Features
 
- - Offer to return Hex codes (6 digits or 3)
- - Offer to return ascii escape codes
- - If the input is text, offer to wrap the input text and return the output as a string
+- **Deterministic** — same input always produces the same color
+- **Pluggable palettes** — bring your own `ColorSet` or use [simplecolorpalettes](https://github.com/taigrr/simplecolorpalettes)
+- **Multiple output formats** — `color.Color`, ANSI escape codes, true-color terminal strings
+- **String and byte input** — hash strings directly or stream bytes via `io.Reader`
 
+## Install
 
-1. take input as bytes
-1. hash the input
-1. use modulo against the sum to choose the color to return from the subset of colors selected.
+```bash
+go get github.com/taigrr/colorhash
+```
+
+## Usage
+
+### Hash a string to a color
+
+```go
+import (
+    "github.com/taigrr/colorhash"
+    "github.com/taigrr/simplecolorpalettes/palettes/html"
+)
+
+palette := html.GetPalette() // or any ColorSet
+c := colorhash.StringToColor(palette, "username")
+// c is a deterministic color.Color
+```
+
+### ANSI terminal colors
+
+```go
+fmt.Println(colorhash.Red("error message"))
+fmt.Println(colorhash.Green("success"))
+fmt.Println(colorhash.BIYellow("bold high-intensity yellow"))
+```
+
+### Automatic color from a palette
+
+```go
+sp := colorhash.CreateStringerPalette(false, false, palette)
+colored := sp.GetString("username") // wraps "username" in its assigned color
+```
+
+## License
+
+0BSD