A readable V3 child may have no own descriptor, an unknown descriptor version,
or multiple descriptors. Those states do not provide a unique discovery fact,
but they do not make the parent or the retained child history unreadable.
Rejecting the entire parent prevented otherwise valid V3 Sessions from opening.
Append a missing parent catalog row only for exactly one supported own child
descriptor. Keep existing parent entries and every child record when no fact is
available. Retain rejection of mismatched creation times, unambiguous mode/label
conflicts, malformed known fields, unreadable membership and revision drift.
Cover raw and compressed read/write publication, preserved source bytes, late
descriptor availability, inherited descriptors and Preview packing. Document
that unavailable discovery evidence can leave a child absent from its parent
catalog and does not trigger automatic backfill after the V4 successor exists.
Extracts the child-evidence behavior from 7ba7e174dd1 and the Preview regression
from 9c85eb60bd25, preserving the original migration authors' work while keeping
message representation and extension interpretation outside this commit.
Co-authored-by: Dudu-0223 <[email protected]>
