Mirrors the menubar prompt-status polygon at fullscreen plus a system-resource readout (CPU/per-core, mem, load, uptime, clock). Shares the menubar's on-disk slab state, read-only. Sandbox-aware for Apple's legacyScreenSaver host: real home via getpwuid (not NSHomeDirectory), no subprocesses (Mach/sysctl/ getloadavg only), never reaps markers. Built with swiftc -emit-library -Xlinker -bundle so no Xcode project is needed. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>