fix: pin @types/node to ^20 and update CI matrix to Node 20 #55

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Final Result: Bugbot completed review and found 1 potential issue.

Request ID: serverGenReqId_3bbba3e3-a6a3-4d04-b63d-0736d1549d66

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

^{Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, have a team admin enable autofix in the Cursor dashboard.}