修复折叠态切换年视图：先展开再切换 + AnimatedContent 尺寸瞬切

折叠态下 toggleYearView 不再直接 return，而是先动画展开回月视图再进入年视图；
MonthHeader 的 AnimatedContent 添加 SizeTransform(snap()) 避免内容切换时尺寸动画；
清理未使用的 import。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

shared/src/commonMain/kotlin/plus/rua/project/CalendarViewModel.kt

@@ -112,9 +112,15 @@ class CalendarViewModel(
      * 当前视图被直接移除；动画只作用在目标视图的 scale/alpha 上。
      */
     fun toggleYearView() {
-        if (isCollapsed) return
         yearViewJob?.cancel()
         yearViewJob = coroutineScope.launch {
+            // 折叠态先展开回月视图，再切换年视图
+            if (isCollapsed) {
+                _collapseAnimatable.animateTo(
+                    0f, spring(dampingRatio = 0.8f, stiffness = 400f)
+                )
+                isCollapsed = false
+            }
             if (isYearView) {
                 // 年 → 月：先启动动画（年视图开始淡出），等一帧后翻转 isYearView（月视图开始组合）
                 composeTraceBeginSection("YearView→MonthView")

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

@@ -36,7 +36,6 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
-import androidx.compose.runtime.withFrameNanos
 import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.runtime.snapshotFlow

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

@@ -1,7 +1,9 @@
 package plus.rua.project.ui
 
 import androidx.compose.animation.AnimatedContent
+import androidx.compose.animation.SizeTransform
 import androidx.compose.animation.core.animateFloatAsState
+import androidx.compose.animation.core.snap
 import androidx.compose.animation.core.tween
 import androidx.compose.animation.slideInVertically
 import androidx.compose.animation.slideOutVertically
@@ -16,12 +18,11 @@ import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.graphicsLayer
-import androidx.compose.runtime.getValue
-import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 
@@ -59,7 +60,7 @@ fun MonthHeader(
                 } else {
                     slideInVertically(tween(250)) { it } togetherWith
                             slideOutVertically(tween(250)) { -it }
-                }
+                } using SizeTransform { _, _ -> snap() }
             }
         ) { (y, m) ->
             Text(
@@ -77,7 +78,7 @@ fun MonthHeader(
                 } else {
                     slideInVertically(tween(250)) { it } togetherWith
                             slideOutVertically(tween(250)) { -it }
-                }
+                } using SizeTransform { _, _ -> snap() }
             },
             modifier = Modifier
         ) { week ->