FindSubStringsAsSectionsW()

FindSubStringsAsSectionsW(pcCondition): enumerate every substring [start, end] and return the sections where the @SubString predicate is TRUE. Engine-backed (stzList.FindW over the candidates), no eval(). FindSubStringsAsSectionsW(pcCondition): the [start,end] sections of every substring matching the predicate. Engine-backed -- enumerates the candidate substrings and evaluates the @SubString predicate via the list W-DSL (stzList.FindW, predicate normalized: { } stripped, @SubString -> @item, Q().Method() lowered), with NO eval(). For engine-expressible predicates (=, or, and, comparisons); for richer ones use the WF form below. Replaces the retired raw-eval FindSubStringsAsSectionsWXT.