Per siax-standard conformance sweep: repo lacked the masterplan-lock CI guard
(.gitea/workflows/masterplan-lock.yml + scripts/check-masterplan-lock.sh) and a
repo-local PLAN/MASTERPLAN_INDEX.md. Copied from sax3l/st0re template (generic
POSIX sh check), stub PLAN index with locked architecture principles and
pointer to sax3l/siax-masterplan.
Refs: sax3l/siax-standard (conformance sweep 2026-09-10)