Skip dead zones in FuzzyMatchV2 score matrix computation

In Phase 3 of FuzzyMatchV2, when a cell's left neighbor score is <= 1
and the current character doesn't match the pattern character, the
cell's score is guaranteed to be 0 (since gap penalties are -1 and -3).
Skip the bonus/gap computation entirely and fast-forward through
consecutive non-matching characters in the dead zone.

This yields 6-11% faster fuzzy searches on typical workloads.

src/algo/algo.go

@@ -569,7 +569,27 @@ func FuzzyMatchV2(caseSensitive bool, normalize bool, forward bool, input *util.
 		Hdiag := H[row+f-f0-1-width:][:len(Tsub)]
 		Hleft := H[row+f-f0-1:][:len(Tsub)]
 		Hleft[0] = 0
-		for off, char := range Tsub {
+		for off := 0; off < len(Tsub); off++ {
+			char := Tsub[off]
+			// When the left neighbor's score is 0 or 1 and the current character
+			// doesn't match, the score is guaranteed to be 0 (gap penalties
+			// are negative). Skip all the bonus/gap computation.
+			if pchar != char && Hleft[off] <= 1 {
+				Hsub[off] = 0
+				Csub[off] = 0
+				// Fast-forward: Hleft of the next cell is the Hsub we just
+				// wrote (0), so only a match can break the dead zone.
+				off++
+				for off < len(Tsub) && Tsub[off] != pchar {
+					Hsub[off] = 0
+					Csub[off] = 0
+					off++
+				}
+				off--
+				inGap = false
+				continue
+			}
+
 			col := off + f
 			var s1, s2, consecutive int16