Review 004 item 15: the unsafe { ctx.get_connection() } UDF blocks
carried no SAFETY justification. Added the concrete soundness
invariant at all ten sites (the eight attach_alkstore_functions
registrations, the notify registration, the test-module savepoint
probe — same class) and registered the comment-only change as
PROVENANCE delta D-40 per ADR-012 §3's diff-fidelity posture.
Task: sqlite-substrate-safety-comments