Problem

Archive.org launched a new passwordless (OTP) registration flow. Since OL and IA share credentials via the xauthn API, users who register on archive.org via OTP receive a randomly-generated password by default. These users are currently unable to log into OpenLibrary — they would need to manually reset their password unless OL implements OTP login.

Proposal

Add OTP login support to OpenLibrary's login page using the ia-otp-form web component from internetarchive/elements (demo/docs), wired through the shared xauthn API.

Dependency

PR #11052 (xauthn scaffolding, related to #10262) must land before this work begins — it introduces the underlying xauthn verify/activate support that OTP login depends on.

Requirements Checklist

• Integrate ia-otp-form from internetarchive/elements into OL's login page
• Wire the OTP flow to xauthn (same API used by archive.org)
• Users who registered via OTP on archive.org can successfully authenticate on OpenLibrary
• No regression on standard password-based login

Stakeholders

• @jimchamp — lead (staff required)
• @rebecca-shoptaw — key stakeholder (built the OTP registration side on archive.org)