1.0.0

Added

• Miku as a native Codex custom pet, built from the original pixel-art sprites of CharlesWiiFlowers/MikuPet. Every cell comes from a real MikuPet frame — cropped, integer-scaled with nearest-neighbour, padded and rearranged; nothing was repainted or generated.
• The installable package dist/miku/: pet.json, spritesheet.webp and CREDITS.txt. Copy the folder into ~/.codex/pets/, refresh the pet list and call /pet.
• A v2 atlas, 1536 × 2288, 8 columns × 11 rows of 192 × 208 cells. Rows 0-8 carry the animation states (idle, running-right, running-left, waving, jumping, failed, waiting, running, review), rows 9-10 the 16 clockwise look directions.
• A v1 atlas, dist/miku_codex_pet_v1.png, 1536 × 1872, for the web upload flow at https://learn.chatgpt.com/docs/pets, which still asks for the shorter sheet.
• tools/build_codex_pet.py — the build script that reads the LibreSprite/Aseprite metadata and PNG strips from src/miku/ and composes the atlases. It takes --source-dir, --dist-dir and --skip-previews.
• Build-time validation that fails the build unless the atlas geometry is exact, every used cell is non-empty and every unused one fully transparent, no transparent pixel carries non-zero RGB, no output exceeds the 20 MiB Codex limit, and every colour already exists in the source sprites — the palette match is what proves no interpolation happened.
• Debug-only motion previews in dist/preview/ and a full frame mapping in dist/build-report.json.
• .github/workflows/release.yml — a manually dispatched GitHub Actions workflow that builds the pet and opens a draft release with miku-codex-pet.zip attached, an archive rooted at a miku/ folder so it unpacks straight into ~/.codex/pets/. The version and the release notes are taken from this changelog, and the tag is created from the built commit when the draft is published.
• Documentation in English and Russian: README.md, README.ru.md, ATTRIBUTION.md and ATTRIBUTION.ru.md, covering the animation mapping, the geometry rules, the known limitations and the provenance of the artwork.