Shifts an OOXML sqref string — a space-separated list of cell references and/or rectangular ranges (e.g. "A1:B2 D4 F1:F10") — under a %ExVEx.Mutation.Shift{}.

Individual tokens that fall entirely inside a deletion span are dropped; partial overlaps clamp to the surviving portion. The returned string preserves the original space-separation order with deleted tokens removed.