No code changes. dist/index.js and dist/index.d.ts are byte-for-byte identical to 9.0.0; only the version number differs.
9.0.0 was published from a laptop because CI could not authenticate with npm, so its tarball carries no provenance attestation and cannot be verified against a commit. npm versions are immutable, so that is not fixable after the fact.
9.0.1 is the same code published from CI with provenance, built from a0bd646 by .github/workflows/release.yaml. You can check it yourself:
npm audit signaturesIf you are on 9.0.0 and do not care about provenance, there is no reason to upgrade.