Breach 0.2.4 (super admins)

Prototype build for super-admin accounts only; hidden from and refused to everyone else server-side.

• The caustic scope follows the admin switch "Breach caustic scope" in /admin/plugin-ui (#362). Close and reopen the Breach window after flipping it. BREACH_SCOPE still overrides for review. CPU reference implementation (~1 s per frame).
• Everything in 0.2.3: Ben's caustic scope and Brine column, light ghost, arp and engine-swap fixes.