utils: export ParseFloat and MustParseFloat wrapping internal utils (#3371)

* utils: expose ParseFloat via new public utils package

* add tests for special float values in vector search

internal/util/convert.go

@@ -0,0 +1,30 @@
+package util
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+)
+
+// ParseFloat parses a Redis RESP3 float reply into a Go float64,
+// handling "inf", "-inf", "nan" per Redis conventions.
+func ParseStringToFloat(s string) (float64, error) {
+	switch s {
+	case "inf":
+		return math.Inf(1), nil
+	case "-inf":
+		return math.Inf(-1), nil
+	case "nan", "-nan":
+		return math.NaN(), nil
+	}
+	return strconv.ParseFloat(s, 64)
+}
+
+// MustParseFloat is like ParseFloat but panics on parse errors.
+func MustParseFloat(s string) float64 {
+	f, err := ParseStringToFloat(s)
+	if err != nil {
+		panic(fmt.Sprintf("redis: failed to parse float %q: %v", s, err))
+	}
+	return f
+}