Combines the two salvaged fixes so they compose instead of conflict:
_persist_session_title (#50575) now writes through set_auto_title_if_empty
(#51483) when the store provides it — the collision-dedup retry and the
manual-/title race protection apply together. Predicate failure (a manual
title landed while generation was in flight) returns None: nothing written,
no callback. Legacy stores without the atomic method keep the plain
set_session_title path, including the vanished-session RuntimeError.
Tests cover both store shapes plus the race-skip path; E2E verified against
a real SQLite SessionDB (collision -> 'Weekly Report #2', manual title
preserved, cron dedup, blank guard). AUTHOR_MAP entry for rasitakyol.
7facf63ae7