Reduce path formatting allocations

internal/engine/path.go

@@ -86,7 +86,20 @@ func (p Path) String() string {
 		return ""
 	}
 
+	// Include each separator and the extra byte introduced by escaping a token.
+	// Use stack storage for sizing indexes without allocating another string.
+	size := len(p.segments)
+	var indexText [20]byte
+	for _, segment := range p.segments {
+		if segment.kind == pathSegmentIndex {
+			size += len(strconv.AppendInt(indexText[:0], int64(segment.index), 10))
+		} else {
+			size += len(segment.key) + strings.Count(segment.key, "~") + strings.Count(segment.key, "/")
+		}
+	}
+
 	var b strings.Builder
+	b.Grow(size)
 	for _, segment := range p.segments {
 		b.WriteByte('/')
 		if segment.kind == pathSegmentIndex {