Topology test must discover local diagram fixtures

Discovery

Upstream tools/test-topology.php hard-codes VibeKB self-hosted diagram ids (self-maintenance-loop, content-load-flow). Installed target repositories like Stoppr fail that test even when their own topologies are valid.

Action taken

Adapted the installed copy to discover a carrier diagram and a known-good topology from the local .vibekb/diagrams/ set (skipping the carrier when asserting the good fixture). Next upstream upgrade may overwrite this file — re-apply or contribute the project-agnostic fix to VibeKB.