v40.9.2

test: migrate from Mocha to Node.js native test runner (#184)

* Migrate test suite to node:test

Replace mocha with the built-in node:test runner. Drop the mocha
devDependency and bump the engines field to require Node 20+, where
node:test is stable.

* chore: consistent use of `node:` protocol on imports

* chore: revert engines bump

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Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: David Sanders <dsanders11@ucsbalum.com>