Writing down what each endpoint actually guarantees made the places it
didn't obvious — shell arguments reaching a crontab or a bash -c
unescaped, master.conf written without tmp+rename, and conf edits that
could be saved without ever being parsed.
Split slow cached monitor endpoint from the live stats. monitor_fast.php
reads /proc/stat, /proc/meminfo, ZFS arcstats, and /proc/net/dev directly
— no cache wrapper, 87ms response. Docker/vm/swap pulled from last full
cache so mem card stays complete. Full monitor poll stays at 2s for
everything else (GPU, containers, storage, etc).