Get a disposable email address (a temporary inbox) for a signup or verification code, with NO Inbin account required at all -- usable before the human has signed up for anything. Returns the inbox address IMMEDIATELY; it does not wait for anything. Use the address to sign up wherever you need a confirmation sent, THEN call await_trial_inbox with that same address to block for the confirmation -- calling this alone does not get you a confirmation. This inbox is NOT tied to any account yet and expires automatically within about two weeks regardless of use. If the human wants to keep using this SAME address permanently, call claim_trial_inbox: no dashboard visit, no key to copy, and more than one agent can independently connect to the same address over time this way.