nextGlobalSequence()/nextSessionSequence() computed MAX+1 with two extra
SELECT round-trips, guarded only by an in-process mutex — two processes on the
same correx.db (CLI + server) could read the same MAX and collide on the unique
index. Compute both the global sequence and session_sequence as MAX+1 subqueries
inside the INSERT and RETURNING the assigned values. SQLite serializes writers,
so the subqueries are atomic across processes; the unique index is the backstop.
Also removes the two pre-SELECTs per append.
kami
65d5e9de83