PUID/PGID (PLEX_UID/PLEX_GID for plex) were 1000:1000 in every definition —
one machine's fact written where it is true of no other (ADR 0112). Each
module now renders identity.env from ${setting:puid} and ${setting:pgid};
the mesh-wide layer carries the image's default, a node whose data belongs
to somebody else says so. An adopted machine's library must never be
re-owned (ace: 1001:2000, hq 153).