What it writes
Select a robot on the floor that has completed at least one delivery, and a button appears: PUT THIS DELIVERY ON-CHAIN. Click it and your own connected wallet is asked to sign a real, zero-value transaction to the project's public settlement ledger address on Robinhood Chain mainnet (chain 4663). The calldata is a plain-text record of the delivery it describes, for example:
Your wallet, your gas
This reuses the same PLUG IN WALLET flow in the header. If you are not connected, the button connects you first; if you are on the wrong network, it asks your wallet to switch to Robinhood Chain; only then does it ask you to sign. The project never holds a key that can spend on your behalf and never pays for anything here: the transaction is yours, from your address, and you need a small amount of RH ETH in your own wallet to cover its gas. If you reject the signature or you are out of gas, the button says so and lets you try again.
Why a transaction, not a toy
Anyone can render a fake blockchain explorer. The point of wiring this to mainnet is that the result is checkable by a stranger: the transaction has a real hash, sits in a real block, and stays there. It costs real, tiny gas, because that is what makes it real, and it costs you the visitor that gas, not the project.
Because every settlement lands at one ledger address, the full set of settlements is public and enumerable: anyone can list them from the explorer API and reproduce, byte for byte, the list of addresses that have settled. That list is the criteria for the settlement airdrop. The scanner that builds it ships in the repo as scripts/airdrop-scan.mjs.