fix(scale-ruler): 修复刻度尺网格计算逻辑

- 调整 extraGridCount 计算方式，确保其为偶数
- 修正网格索引计算中的语法错误，统一使用空格分隔运算符
- 优化刻度尺渲染精度，提高视觉对齐效果

src/components/scale-ruler.vue

@@ -48,7 +48,7 @@ const currentValue = ref(Math.round(props.initialValue || props.min))
 const totalUnits = computed(() => Math.round((props.max - props.min) / props.step))
 
 
-const extraGridCount = Math.ceil((uni?.getSystemInfoSync?.().windowWidth || 375) / props.gutter)
+const extraGridCount = Math.ceil((uni?.getSystemInfoSync?.().windowWidth || 375) / props.gutter / 2) * 2
 
 const gridList = ref<GridItem[]>([])
 const totalWidth = ref(0)
@@ -59,7 +59,7 @@ function buildGrid() {
   const count = totalUnits.value
   const arr: GridItem[] = []
   for (let i = 0; i <= count + extraGridCount * 1; i++) {
-    const numIndex = i - extraGridCount /2
+    const numIndex = i - extraGridCount / 2
     const num = props.min + numIndex * props.step
     const displayNum = num
     const isLongGrid = (numIndex % 10 === 0)