test(index)!: use partialDeepStrictEqual

[Fdawgs]

BREAKING CHANGE: minimum node version increased from 20 to 22.17.0

Not in a massive rush to merge this as it's just for tests and not functionality.

Checklist

• Run npm test
• Commit message adheres to the Conventional commits style, following the @commitlint/config-conventional config

[Copilot]

Pull request overview

Updates the unit test suite to use Node’s assert.partialDeepStrictEqual via node:test, and aligns repository tooling with a higher minimum Node.js version.

Changes:

• Replace the custom matchObject helper with t.assert.partialDeepStrictEqual in the unit test.
• Bump the declared Node.js minimum version to >=22.17.0 and update local/dev tooling (.nvmrc, devcontainer).
• Update CI to stop running tests on Node 20.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/index.test.js	Removes custom subset assertion helper and uses partialDeepStrictEqual in the header assertion.
package.json	Raises engines.node minimum to >=22.17.0.
.nvmrc	Pins local Node version to 22.17.0.
.github/workflows/ci.yml	Removes Node 20 from the unit test matrix.
.devcontainer/devcontainer.json	Updates devcontainer base image from Node 20 to Node 22.

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