smix-annotate 0.3.1

smix-annotate — screenshot annotation library. Composes circle / arrow / text / box / line primitives over PNG bytes with named color palette and 3-preset PNG compression. Powers `smix annotate` / `smix screenshot --annotate` CLI + `takeScreenshot: {annotate: [...]}` yaml verb + `--debug-output` fail-step auto-annotate. RFC v0.3.0 (docs/ai-guide/rfc-v0.3.0-annotated-screenshots.md).