feat!: rewrite color engine with terminal detection and downsampling

[MarvinJWendt]

Requested by Marvin · project thread

Before: color printed escape codes whatever the terminal could show. A pipe or a file got raw codes, an RGB color on a 16-color terminal came out wrong, and the package shipped its own Success/Error styles.

After: every print checks the writer it goes to. Piped output is plain, RGB colors are converted to the closest color a 256 or 16 color terminal can show, and the package only does color and text attributes. PTerm v0.13 builds on it.

How: the engine is PTerm's internal color code moved here. Detect(w) reads FORCE_COLOR, CLICOLOR_FORCE, NO_COLOR, CLICOLOR, checks whether w is a terminal, then reads COLORTERM, TERM and TERM_PROGRAM, and on Windows turns on ANSI processing in the console. Background(timeout) reads COLORFGBG or sends an OSC 11 query followed by DA1, so terminals that do not answer OSC 11 return at once instead of waiting for the timeout.

API

• Color: one comparable value type. Red ... BrightWhite, Index(n), RGB(r, g, b), Hex(s), MustHex(s), Parse(s) (hex, names, 0-255, "none"). Methods RGB, Hex, String, Mix, Luminance, IsDark, Fg, Bg, Sprint.
• Style{Foreground, Background, Attrs} with New(attrs...), Fg, Bg, Add, Bold and friends, Sequence(level), Render(level, text), Sprint/Fprint/Print variants. Render handles nesting and styles each line separately.
• Level: LevelNone, LevelBasic, Level256, LevelTrueColor. Detect(w), DetectEnv(), IsTerminal(w), SetLevel(l), ResetLevel().
• Strip, Hyperlink, SGR, Background.

Breaking changes

• Mode, ANSIColor, ANSI256Color, RGBColor, the Color interface, NoColor, NewColorFromRGB, NewColorFromHex, NewStyle, Modifier and color.Writer are gone. Use Color, Index, RGB, Hex, None, Style and Attr.
• The predefined styles (Success, Error, Green(...) and so on) are gone.
• Go 1.27 is required. New dependency: golang.org/x/term.

Tests: go test -race ./... passes, golangci-lint reports 0 issues for linux and windows.

🤖 Generated with Claude Code

https://claude.ai/code/session_011Dno7CsMx2fSzNx5ZTm7RL

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