v19_bridge_out

Bridge out: withdrawals from Sunima back to Arbitrum, signed by a validator threshold key group (BRIDGE_OUT, 67 %, no single key holder). New on-chain FROST signing sessions in x/threshold_signatures; x/bridge mirrors the bridge contract from storage proofs, burns withdrawn tokens and refunds only by proof (a signed exit can never be refunded twice). Contract governance actions are typed, delayed and vetoable. Withdrawals stay closed until governance opens them per token. Validators: keyd and bridge-watch get new message grants after the upgrade. Release and checksums: https://sunima.uk/chain/upgrades/v19_bridge_out/