ParseWindowLookup

ParseWindowLookup converts a lookup path into a concrete window filter. Paths traverse generated JSON relation names and separate segments with double underscores. The default operator is exact. Accepted suffixes are eq, exact, iexact, contains, icontains, startswith, istartswith, endswith, iendswith, in, nin, regex, and iregex; availability is field-specific. The eq suffix aliases exact, nin negates in, scalar operators require one value, and in and nin require one or more. Invalid paths, operators, values, or results wrap ErrInvalidFilter.