signing_identity/1 returns the handle's pub A; sign/2 signs with a DIFFERENT key B. The verify_signature guard in the shared tail catches the sign/2-vs-snapshot mismatch -> :signing_failed.
signing_identity/1 returns the handle's pub A; sign/2 signs with a DIFFERENT key B. The verify_signature guard in the shared tail catches the sign/2-vs-snapshot mismatch -> :signing_failed.