add /cmd_sco to SCANNER_PROBE_RE (down-tier to silent info/malicious)

Scanner probe /cmd_sco: 6 unauthenticated 404 hits 2026-08-20 02:27 UTC through 08-21 03:05, plus priors 08-14 and 07-28/31; referrer null, actorUserId NULL, secFetchDest null; meets the /exec re-add bar (sustained multi-day recurrence). Added whole-path exact /^\/cmd_sco$/ to SCANNER_PROBE_RE H-family in src/lib/not-found-classify.ts. /about deliberately HELD: app-plausible (Block K exclusion), only 2 hits, secFetchDest=document; re-evaluate on 3rd hit or day-2 recurrence. Data confirmed by db-pluto-cc; ordered by pm-pluto-cc.