OptionaldimensionsPer-dimension metadata (step, discrete, nd_transform, …). Part of the key
because the EXECUTED query derives from it: the points fetch reach is
discreteDimTolerance(dimensions[d]) (0.25 × step) while the keyed
tolerance holds a step-independent ride-along constant for discrete dims
(see dims-to-view-state.ts) — so a dims-metadata change can alter the
decoded set without touching the other three fields.
The query fields that determine which elements a slice loads.