tests/test-omp-compat.mjs skipped whenever omp was not on PATH, which
was always the case in CI, so 0.6.1 shipped an import that pi's compat
entrypoint provides but OMP's bundled pi-ai does not (#74).
Add an omp-compat job that installs @oh-my-pi/pi-coding-agent with Bun
and runs the suite with OMP_COMPAT_REQUIRED=1, which turns the skip into
a failure. Add a first phase that loads the extension through
`omp models -e`, the same loader `omp plugin install` validates with;
it fails on the 0.6.1 index.ts and passes with the runtime resolution.
Patrick Wozniak