docs: update documentation for passkey MFA feature

- Add V002/V003 migrations and VendorAuthPolicy classes to CLAUDE.md
- Document MFA & passkey enforcement model in config CLAUDE.md
- Mark passkey MFA design spec as Implemented

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-04-27-passkey-mfa-design.md

@@ -1,7 +1,7 @@
 # Passkey MFA Design
 
 **Date:** 2026-04-27
-**Status:** Draft
+**Status:** Implemented
 **Goal:** Add passkeys (WebAuthn) as an MFA factor alongside existing TOTP, with a long-term path toward passwordless sign-in.
 
 ## Motivation