The /admin layout had three nested concentric shells: the global Shell
header + main nav, then a per-admin header banner with a Sword icon, then
a left-aligned admin sub-nav (AdminSidebar) — two competing left-edge
navigation columns plus a redundant 'Admin' label that the URL and active
nav already conveyed.
Replaces the side sub-nav with a horizontal tab strip across the top of
the admin content (matches the discover-page tab pattern), drops the
duplicate header banner, and removes the disabled Users/Library
placeholder items so the tab strip only shows surfaces that actually
ship today. The component is renamed AdminSidebar -> AdminTabs to match
its new shape.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen
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