Fix billion suffix logic and use new Array()

Co-authored-by: hckhanh <[email protected]>

Author: Copilot

src/read/groups.ts

@@ -31,9 +31,9 @@ function getUnitSuffix(
 
   if (type === 3) {
     // Billion: repeat "tỷ" based on position (position 3 = "tỷ", position 6 = "tỷ tỷ", position 9 = "tỷ tỷ tỷ", etc.)
-    if (positionFromRight >= 6 && hasTrailingZeros) {
+    if (positionFromRight >= 3 && hasTrailingZeros) {
       const billionCount = Math.floor(positionFromRight / 3)
-      return ' ' + Array(billionCount).fill('tỷ').join(' ')
+      return ' ' + new Array(billionCount).fill('tỷ').join(' ')
     }
     return ' tỷ'
   }