Each test serves its own CA_LIST.cer through the working-directory
override of the sandbox path. guest_ssl_system_roots checks that a
handshake to the fixture server fails without the helper and passes
with it, that a context authority still works alongside the list, and
that an empty or certificate-free list throws with its path.
guest_http2_system_roots sends a request from a context with no loaded
certificate, which passes only through the transport's helper call.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
