B20 Metadata Integrity

🆕 A B20 with a METADATA_ROLE holder can call updateName/updateSymbol — change its own identity after launch (an impersonation / bait-and-switch vector ERC-20 has no protocol equivalent for). Reads whether the metadata is mutable (role holder exists) AND whether it has ALREADY been renamed on-chain (NameUpdated/SymbolUpdated history). Trust the address, not the label.