5f342b0b4e
The DM/group thread queries used `(? IS NULL OR created_at < ?)` — an all-NULL
param Postgres can't type ('could not determine data type of parameter') — and an
unaliased FROM-subquery (Postgres requires an alias). Both rewritten to add the
`created_at < ?` clause only when a cursor is given, and alias the subquery `t`.
Portable; sqlite db-smoke still 22/22.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>