FileKeySource rejected any key file whose mode had group or other bits,
but Windows has no such bits: Stat reports every writable file as 0666.
On the Windows builds release.yml ships, the key file therefore never
loaded, not even one written 0600, and only XUI_NODE_TOKEN_KEY could
supply a key. The mode check now applies off Windows only, the stance
the DB permission tests already take; there the file's NTFS ACL guards
it, and env-vars.mdx says so in all four locales.
The load test is split so the half that must hold everywhere, an
owner-only file loading, also runs on Windows, and the rejection half
asserts the exact error instead of any error.
MHSanaei