OWL lock screen needs to know (a) the active session mode (legacy or
session_swap) to branch between endpoints, and (b) the kiosk uid to
determine 'is the current browser session the kiosk?' Both come from
the bootstrap response so no extra round-trips on every render.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>