Fold the writer-claim fence into the four sync write ops at their
definition sites, collapse the logical-layer fence wrappers to plain
re-exports, delete the session-accessor.sqlite middle barrel (the only
unfenced escape hatch), and retarget its 26 importers to the focused
defining modules. replaceSessionEntrySync intentionally stays unfenced:
its two production callers own their freshness guards and its return
carries no rebound signal. Net -106 production LOC, behavior-neutral.
Part 1 of the session-accessor dual-layer collapse.
Peter Steinberger
23d1eca455