The available strike modes, in display order.
Preferred mode pointers, most-preferred first; absent
(undefined/null) and no-longer-available entries are skipped.
Extracts the effective mastery level of a mode (the best-chance tiebreak).
The index of the default mode in modes, or -1 if modes is empty.
The default mode index for a picker: the first of
preferencesthat is still available, otherwise the best-chance mode (highest effective ML). Pure.