frame_mods runs on the Frame, but the server tests import it on every
desktop OS; the module-level `import fcntl` failed test discovery on
Windows. Import it where the lock is taken, as frame_panels and frame_vr
do. Skip the Frame-side helper tests on Windows, as test_input does for the
input agent: they rely on /proc, flock and POSIX prefix paths. The server
routes and the usage-error check still run there.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
