Migrate the container relations write actions onto lib/relations: POST
/internal/actions/attach-child + /detach-child dispatch to relations/relate
and relations/unrelate over the same "type:id" node model, behind the
auth+ACL pipeline (wrap-errors . require-auth . require-permission), mirroring
POST /feed. Closed-loop test: attach -> visible via get-children -> detach ->
gone; 401/403/400 guards. Ledger now models the full relations surface (7
endpoints): container reads+writes migrated, typed relate/unrelate/can-relate
proxied (registry+cardinality validation not in lib/relations). Off-Quart
coverage 45% -> 50%.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
giles
bac80f6c0b