Shared editorial nav function component for all four KB LiveViews.

Renders a persistent horizontal sub-navigation with three links: Knowledge base, Suggestions, Gaps.

Usage: <.kb_nav current={:index} /> <.kb_nav current={:suggestions} /> <.kb_nav current={:gaps} /> <.kb_nav current={:editor} />

The :editor value renders no active marker — Editor has no top-level nav entry.

All CSS uses bare var(--cl-<token>) — no hex fallbacks (BRAND-04 gate). Active route is paired with aria-current="page" AND a primary border-bottom (never color alone — brand §7.5).