test(matrix): regenerate cargo-expand snapshot for op-qualified index arms

The index-engagement op fan-out (finding-1) changes the macro bodies, so the
int4 cargo-expand body snapshot moves. Regenerated under the pinned nightly
(mise run test:matrix:expand). The diff is confined to the index_engages arms;
non-index arm bodies are unchanged, and the regenerated index arms still carry
the eqlmatrix tag, SET LOCAL enable_seqscan=off, and assert_index_scan_uses —
proof the Stage 2 leaf behaviour survived the driver refactor.

Author: tobyhede