chore: switch corepack and .nvmrc, upgrade to node 20

[chrisgervang]

Aligns Node version management with deck.gl:

• Add .nvmrc pinned to 20.18.0
• Replace volta field with "packageManager": "yarn@1.22.19" in package.json
• Update CI workflow to read node version from .nvmrc and enable corepack
• Remove single-element node version matrix (was just [18])

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Note

Low Risk
Low risk: this only updates tooling/CI Node and Yarn version management, but it could break local dev or CI if any dependency/tooling isn’t compatible with Node 20.

Overview
Switches the repo to Node 20 and standardizes version management by adding .nvmrc (20.18.0) and replacing volta pinning with packageManager: "yarn@1.22.19".

Updates the GitHub Actions test workflow to use actions/checkout@v4 and setup-node@v4 with node-version-file, enables Yarn via Corepack with built-in caching, and bumps the Coveralls action to v2.

Raises the engines.node requirement to >= 20 across the affected workspace packages.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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Corepack must be enabled before setup-node caching

High Severity

The corepack enable yarn step runs after actions/setup-node@v4 with cache: 'yarn', but setup-node needs yarn to be available at its execution time to resolve the cache directory. Since package.json now declares "packageManager": "yarn@1.22.19", the setup-node action expects corepack to already be enabled to locate the correct yarn binary for caching. This ordering will cause the CI workflow to fail. The corepack enable step needs to be placed before the setup-node step.

Additional Locations (1)

• .github/workflows/test.yml#L16-L21