修复月视图首帧行堆叠：rowHeightPx 未就绪时 alpha=0

draw 阶段已读到更新后的 rowHeightPx，但 layout 仍用旧值时会出现行堆叠。
增加 layoutReady 守卫，首帧 rowHeightPx==0 时直接隐藏月视图。

shared/src/commonMain/kotlin/plus/rua/project/ui/CalendarMonthView.kt

@@ -233,6 +233,9 @@ fun CalendarMonthView(
             }
 
             val monthProgress = 1f - viewModel.yearViewProgress
+            // 组合阶段计算：lambda 捕获快照值，避免 draw 阶段读到已更新的 rowHeightPx
+            // 但 layout 仍用旧值导致行堆叠
+            val layoutReady = rowHeightPx > 0
             Box(
                 modifier = Modifier
                     .fillMaxSize()
@@ -240,7 +243,7 @@ fun CalendarMonthView(
                         val scale = lerp(0.3f, 1f, monthProgress)
                         scaleX = scale
                         scaleY = scale
-                        alpha = monthProgress.coerceIn(0f, 1f)
+                        alpha = if (layoutReady) monthProgress.coerceIn(0f, 1f) else 0f
                         transformOrigin = TransformOrigin(anchorPivotX, anchorPivotY)
                     }
             ) {

shared/src/commonTest/kotlin/plus/rua/project/CalendarViewModelTest.kt

@@ -18,7 +18,6 @@ class CalendarViewModelTest {
 
     private val fixedInstant = Instant.parse("2026-05-15T00:00:00Z")
     private val testClock = FixedClock(fixedInstant)
-
     private fun createViewModel(): CalendarViewModel {
         val scope = CoroutineScope(Dispatchers.Unconfined)
         return CalendarViewModel(coroutineScope = scope, clock = testClock)