Project memory lives in its project shard, user memory in a per-user shard

On the lean ledger, a project’s memory lives in that project’s shard (its catalog a writer projection there) and user-level memory in a per-user scope shard; there is no separate memory shard, and legacy memory is read once into the shards, after which the legacy file has no memory writer. One substrate for both (UR-01, UR-04); refines MEM-DIR and UD-S2.