Records the config boundary the #127 owner-default columns establish:
.env = boot-time deployment config + secrets (never DB), user_ai_prefs
single row = per-request owner defaults (hot-tunable, no secrets),
resolution request param -> owner default -> hard default, and the
safe-by-default privacy posture for default_backend. Adds the
Configuration glossary section to CONTEXT.md (owner default,
deployment config, hard default).
