Offline Signature Verifier

Recovers the address that produced a signature, for both personal_sign messages and EIP-712 typed data, using pure arithmetic with no network access whatsoever. It shows the digest alongside the result, because the most common reason a valid signature appears wrong is verifying text that differs from what was signed — a trailing newline is enough. Typed-data payloads have EIP712Domain stripped from their types map automatically, since leaving it in is the usual reason a pasted payload refuses to verify. High s values are flagged: a mirror signature recovers to the same address, which is why EIP-2 rules them out and why contracts that accept them can be replayed.