0.4.6: maker-slice trade accounting, maker production receipt

trades_totals no longer overcounts MAKER-role fills (V2 bundles multi-maker matches into one record; we now sum only our maker_orders slices, matched by funder). Found live while producing the maker receipt now shown in the README: limit_gtc posted above the bid, matched as MAKER at zero fee, settled on-chain. Real settlement record ships as the test fixture.