[test]: full suite is not clean on declared Node 20 minimum

[pitimon]

Problem

The package declares Node.js >=20, but the complete test suite is not clean under Node 20.20.2.

Observed during independent review of PR #162:

• Goose focused and WAL/reset tests pass on Node 20.
• Full node --test test/*.test.js fails in unchanged test infrastructure:
  • a parser-conformance fixture imports node:sqlite, unavailable in Node 20;
  • the TypeScript guardrail's nested npm exec invocation fails in the Node-20 test environment.

Expected

Either:

1. Make the full test suite execute successfully on the declared minimum Node 20 runtime, replacing/guarding node:sqlite fixtures and making nested TypeScript invocation portable; or
2. Raise the declared minimum Node version and align release workflows/documentation.

Add a Node-20 CI matrix job so engine compatibility is continuously enforced.

This is pre-existing and was not introduced by PR #162.