Upgrade vitest to clear the @vitest/mocker path-traversal advisory #11

The push to main for #10 reported one open Dependabot alert: a moderate path-traversal advisory in the development dependency vitest (@vitest/mocker, "Redirect Mock"). It predates the release-tags change and only affects the test runner used in this repository's own CI and local runs.

Fix: upgrade vitest (and @vitest/mocker if pinned) through the package manager, within the repository's release-age gate, and confirm the alert closes.

Deferred because the 3.0.0 release and its consumer changes came first. Revisit trigger: the next change to this repository, or before the next release.