Bug: @simplewebauthn v13 changed credential.id from Uint8Array to
base64url string. Buffer.from(string) without encoding stored the
ASCII text instead of decoded bytes. Authentication then failed to
match because it correctly decoded with "base64url".
Fix: Buffer.from(credential.id, "base64url") in both registration
and add-passkey flows.
Also: catch WebAuthn "not allowed" errors and show a friendly message
instead of the raw browser error.
Existing passkeys must be re-registered after deploy.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
