tuist setup cache handles logged-out state correctly

Running tuist setup cache while logged out no longer installs a daemon that immediately loops. Setup now checks authentication up front and aborts with a clear instruction to log in. The cache-start daemon itself exits cleanly when there are no credentials, and the launchd agent now only respawns on a crash instead of on every clean exit, so logged-out machines no longer see a respawn every ~10 seconds or accumulate empty session directories. Authenticated setups and the CI TUIST_TOKEN path are unaffected.