A store is written v3 (v5 for a directory) only when a record in it holds a non-empty
element id. CultElementIds.Plan reports that as IdPlan.HoldsIds; the admission stamps it
on the stored record and every store reads it. The descriptor's CarriesElementIds is
deleted. A file already marked on disk stays marked. CultPersistedStoreSnapshot.FormatFor
is the one header decision.
Plan refuses one element object sitting twice in a list at write, naming the record and
list, instead of writing both ids and refusing the store at load.
CultMesh single-file write mints, refuses and marks as a cache write does; the read applies
the load-time plan, so a write and a load refuse the same things.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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