Right above the CLI download link on that page, there's a warning icon with "Authenticate with Antigravity or Antigravity IDE before using the CLI."

Ok, I guess this is outdated then because I did what I said I did.

	▲	dgacmu an hour ago \| parent [-]
		Ah! You're right, I just re-tested on my server and was able to get it to work now. Thank you! Does appear to just be stale documentation.