Optional capability a ContractHandler implements to participate
in wallet.restore()'s gap-limit scan. The scanner owns the index
loop and the gap counter; the handler answers "do I own a contract
anchored to the pubkey/descriptor at this index?" — checked against
the indexer / explorer / (for swaps) the handler's own source. The
handler MAY batch/cache internally across calls.
Optional capability a ContractHandler implements to participate in
wallet.restore()'s gap-limit scan. The scanner owns the index loop and the gap counter; the handler answers "do I own a contract anchored to the pubkey/descriptor at this index?" — checked against the indexer / explorer / (for swaps) the handler's own source. The handler MAY batch/cache internally across calls.