Transaction.GetInterchain and Block.GetInterchain take variadic options
(client.WithPerChain / client.WithChains, re-exported as sdk.WithPerChain /
sdk.WithChains) that map to the new prime-node ?perChain=&chains= query params.
Backward compatible: existing no-option calls get the default (one anchor per
chain). client.InterchainQuery builds the suffix; unit-tested.
