Test-only helpers shared across the workspace: golden-file harness, the testscript runner used by the integration
suites, temp-directory and free-port allocators, and small assertion utilities. Production code does not depend
on this crate; only [dev-dependencies] and the dedicated testsuite/ repository do.
Test scripts here run RQL through the embedded engine; their inputs and outputs are checked against goldenfiles
that live in testsuite/. Regenerating those goldenfiles is a deliberate manual operation, never an automatic
one in this crate.