fix(sdk-coin-sui): handle epoch round trip

[abhishekagrawal080]

TICKET: CSHLD-601

TransactionExpiration with an Epoch value could not round-trip through BCS serialization/deserialization.

When txBuilder.expiration({ Epoch: 324 }) was used and the transaction was built, the BCS bytes were correct. But factory.from(rawTx) (via TransactionDataBlock.fromBytes()) threw a StructError because the deserialized value was { Epoch: 324n } and validation expected object({ Epoch: integer() }).

Root cause:

sui-bcs.ts registers TransactionExpiration.Epoch as BCS.U64

@mysten/bcs deserializes U64 as BigInt at runtime

TransactionDataBlock.ts validated the deserialized value with object({ Epoch: integer() })

superstruct's integer() accepts JavaScript number but rejects BigInt

[linear]

CSHLD-601 Fix `TransactionExpiration` Epoch BCS round-trip failure