fix: allow undoing the first drill move in review

[epinxteren]

Summary

• Allow the back button to return from the first played drill move to the drill starting position.
• Keep navigation stopped at that starting position.

Validation

• Reproduced the disabled back button on the live drills page after the first move.
• The changed file passes ESLint; git diff --check passes.
• Repository-wide lint and TypeScript checks hit an unrelated existing COPY_AUTOCAPTURE_EVENT import error in src/lib/posthog-browser-config.ts. npm ci is also blocked by the current lockfile being out of sync.

[vercel]

@epinxteren is attempting to deploy a commit to the Maia Platform Team on Vercel.

A member of the Team first needs to authorize it.