Drop the `sys.platform = "darwin"` fake (this file's own convention is
`@pytest.mark.macos_only` for dispatch) and exercise `_macos_osascript`
directly, which is where the furl gate now lives. Parametrize the
has-image contract over an image and a non-image Finder copy so the
extension gate — the fix's false-positive risk — is bound by a test.
228022ef5b