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.