A filter predicate on a scalar column of the main feature table was always
encoded as a self-semi-join (A.id IN (SELECT A.id FROM <main> WHERE ...)).
That subquery scans the whole table and the planner does not flatten it, so
its cost grew with the table size rather than with the number of selected
features. Such predicates are now emitted as a direct conjunct on the main
alias. The semi-join form is kept whenever evaluating the predicate requires
a join, junction, or array traversal, where it is load-bearing for
cardinality.

This also fixes a latent bug in the temporal interval (OVERLAPS) encoding,
which hardcoded a trailing parenthesis to close the self-semi-join subquery;
it now preserves the operand expression's suffix so both the inline and the
subquery forms stay balanced. A negated inline predicate is wrapped as
NOT (...).

Updates the golden SQL specs and query fixtures accordingly.