Add "Other primitives — quick reference" section (between StatusPill
and Rules) covering primitives that had no code examples before:
LoadingBackdrop, SwitchSimple, PrimaryLinked, DashedBreakline,
TabPannel+activeStyles, LargeOptionPicker, Timer, ErrorBoundary,
NotificationAlert + useNotificationContext API.

Each shows import, canonical usage, conventions, and when NOT to
use (which alternative fits instead). Listed in descending consumer
usage order.

Bump 0.6.2 -> 0.6.3 (docs-only).