Fix release verification step failing on a missing import

[epalosh]

The v0.2.2 release build (run 31911018012) reached the new install-and-verify gate and failed with:

ModuleNotFoundError: No module named 'openfov'

The build job installs requirements-dev.txt but never pip install -e . — only the CI workflow does — so the package wasn't importable when the step called ensure_registered().

Fixed by setting PYTHONPATH for that step only, rather than adding an editable install to the job. An editable install would land before the ~35 minute Nuitka build and change the environment it resolves imports in; not worth that risk to satisfy one verification step.

What the gate proved before it broke

Everything up to the import passed on a real runner:

• ✅ NPClient + hardened TrackIR shim built with the version resource
• ✅ Nuitka standalone build
• ✅ Inno Setup installer built
• ✅ Installer installed silently with exit 0
• ✅ Both NPClient64.dll and TrackIR.exe present in C:\Program Files\OpenFOV\resources\bin

And it correctly refused to publish — no release, no artifact upload. Nothing broken shipped.

Verified locally

The exact failing command now succeeds:

$ OPENFOV_BIN_DIR="C:\Program Files\OpenFOV\resources\bin" PYTHONPATH=src \
    python -c "from openfov.output.npclient_bootstrap import ensure_registered; ensure_registered()"
ensure_registered OK (exit 0)

No v0.2.2 release exists, so once this merges the v0.2.2 tag can be moved to the new commit rather than burning a version number on a CI-only fix.