A record's bytes cannot say whether it holds an element id (an id is an ordinary keyed
string), so the per-record fact decoded by whichever type loaded the record was a split
authority: a narrower type unmarked a v3 store over bytes holding ids. HeaderForWrite is now
a pure function of the durable header, the HoldsIds of the records the write encodes, and
whether it copies any record forward: a write that copies keeps a marked header, a write
that encodes every record decides by content. The directory store takes the same rule.
Also pins the three Low test findings deferred from c2a-write-set s3: the reload cause is
observed by type and message, the author's own Expect after a commit, and the directory
store's re-mint branches.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>