Add release automation and npm package metadata

[AdrianOrlow]

Motivation

• Automate publishing the built library to npm on pushes to main and provide a predictable package layout and versioning for consumers.
• Ensure the built JS, type declarations and CSS are exported from the package so consumers can import components and styles from @gi-org-pl/athena.

Description

• Add GitHub Actions workflow .github/workflows/release.yml that installs deps, builds, prepares a release version, and runs npm publish using NODE_AUTH_TOKEN on pushes to main.
• Add scripts/set-release-version.mjs which sets package.json to a unique 0.0.0-main.<run>.<attempt> version using GitHub Actions run metadata.
• Update package.json to publish as @gi-org-pl/athena, expose ./dist/athena.js, ./dist/main.d.ts and ./dist/athena.css via exports, add files/publishConfig/repository metadata, and add the release:version script.
• Include the compiled CSS in the library entry by importing ./index.css in src/main.ts and document installation/usage in README.md.

Testing

• Ran npm run build which produced dist/athena.js, dist/athena.css, and dist/main.d.ts (succeeded).
• Ran lint via npm run lint (calls npx @biomejs/biome lint) and it completed with no issues (succeeded).
• Ran GITHUB_RUN_NUMBER=123 GITHUB_RUN_ATTEMPT=2 npm run release:version to verify version generation and it printed the prepared package version (succeeded).
• Ran npm pack --dry-run to validate the packaged files list and tarball metadata (succeeded).

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Codex Task

[github-actions]

Coverage Report

Coverage after merging codex/fix-issue-102-and-create-pr into main will be:

	Hit/ Total	Coverage
🟰 Statements	335 / 335	100% 🥳
🌿 Branches	412 / 412	100% 🥳
🔢 Functions	87 / 87	100% 🥳
📝 Elements	834 / 834	100% 🥳