test: validate published package contract

[okyrychenko-dev]

Summary

• add repeatable packed-package verification following the type-utils conventions
• compile packed declaration consumers under ESM and CommonJS resolution
• verify ESM and CommonJS runtime entry points
• correct conditional exports so CommonJS resolves index.d.cts
• validate packed files, runtime dependencies, peer dependencies, and exports
• verify sideEffects: false independently of package metadata
• measure ESM, CommonJS, declaration, and minimal-consumer sizes
• add attw and publint package inspection
• run package verification in CI and the release contract
• include formatting, scripts, and Storybook in release verification

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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