fix(supervise): share auth keys between supervise and user create

[manavjaiswal]

This change makes node space supervise use the same default auth-key store as node space user create, so password verifiers created by the CLI can be opened by the running supervised server.

What changed:

• supervisor auth-key loading now reuses the shared server-side auth loader
• node space supervise help/docs now describe the shared auth-store behavior
• added a regression test for the default auth-key source

How to test:

1. Start from a clean checkout.
2. Set CUSTOMWARE_PATH to a real absolute path.
3. Run node space user create <username> --password <password> --groups _admin.
4. Run node space supervise HOST=127.0.0.1 PORT=3000.
5. Open the browser at http://127.0.0.1:3000 and log in with the user you created.
6. Confirm the login succeeds without having to copy auth keys manually.

Regression coverage:

• node --test tests/supervise_command_test.mjs

Fixes #52