Rewrite help panel to use the same grouped navigation pattern as the
admin aside panel (details/summary with nav links). Remove inline
keyboard shortcuts table and about section. Panel now shows
permission-gated navigation groups: Documentation (docs viewer, API
docs) and System (system info). Remove custom CSS — panel inherits
existing app-sidebar-admin-nav styling.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>