Measurement of $C\!P$ asymmetries and branching-fraction ratios for $B^\pm \to DK^\pm$ and $Dπ^\pm$ with $D\to K^0_{\rm S} K^\pmπ^\mp$ using Belle and Belle II data

We measure CP asymmetries and branching-fraction ratios for B-+/--> DK(+/-)and D pi(+/-)decays with D ->(KSK +/-)-K-0 pi(-/+), where Dis a superposition of D-0 and D-0. We use the full data set of the Belle experiment, containing 772 x 10(6) B B ($) over bar pairs, and data from the Belle II experiment, containing 387 x 10(6) BB ($) over bar pairs, both collected in electron-positron collisions at the Upsilon(4S)resonance. Our results provide model-independent information on the unitarity triangle angle phi(3).