Numbered Accounts: proposal of a new address format & wallet contract interface

Numbered Accounts is a rough proposal for a new address format and wallet contract interface that would interoperate with existing Ethereum accounts while limiting each account to a single chain and, optionally, specific assets. Addresses take the form routing number plus account number, such as 1001-123, where a singleton RouteRegistry contract on mainnet maps each routing number to a bank contract on a chosen chain. The author argues this reduces wallet complexity and user error, since an account cannot receive unsupported assets or assets on the wrong chain. Bank contracts would support transfers in, out, and between numbered accounts, with the stated goal of integrating with ERC-4337.