feat: 使用 AnimatedContent 平滑切换 CalendarPager ↔ WeekPager

- 用 AnimatedContent 包装 pager 切换，添加 fadeIn/fadeOut 过渡
- 延迟 50ms 切换避免折叠 spring 动画期间的视觉跳跃
- 修复 WeekRow 下方行的 yOffset 计算（移除 phase2 项）
- WeekPager 添加农历缓存支持
- 添加折叠动画调试日志

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

core/src/main/kotlin/plus/rua/project/CalendarViewModel.kt

@@ -20,8 +20,11 @@ import kotlinx.datetime.plus
 import kotlinx.datetime.todayIn
 import plus.rua.project.ui.COLLAPSE_THRESHOLD
 import plus.rua.project.ui.getMonthGridInfo
+import android.util.Log
 import kotlin.time.Clock
 
+private const val TAG_VM = "CalendarExpand"
+
 /**
  * 日历日期数据，用于网格单元格渲染。
  *
@@ -285,7 +288,9 @@ class CalendarViewModel(
      * @param delta 拖拽增量，已归一化到 [0,1] 区间
      */
     fun onExpandDrag(delta: Float) {
+        val old = _collapseProgress.value
         _collapseProgress.value = (_collapseProgress.value + delta).coerceIn(0f, 1f)
+        Log.d(TAG_VM, "onExpandDrag: delta=$delta old=$old new=${_collapseProgress.value}")
     }
 
     /**
@@ -295,13 +300,16 @@ class CalendarViewModel(
      */
     fun onExpandDragEnd() {
         val progress = _collapseProgress.value
-        if (progress < (1 - COLLAPSE_THRESHOLD)) {
+        val result = if (progress < (1 - COLLAPSE_THRESHOLD)) {
             _isCollapsed.value = false
             _collapseProgress.value = 0f
+            "EXPANDED"
         } else {
             _isCollapsed.value = true
             _collapseProgress.value = 1f
+            "COLLAPSED (bounce back)"
         }
+        Log.d(TAG_VM, "onExpandDragEnd: progress=$progress threshold=${1 - COLLAPSE_THRESHOLD} result=$result")
     }
 
     /**

core/src/main/kotlin/plus/rua/project/ui/CalendarMonthPage.kt

@@ -21,6 +21,7 @@ import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.zIndex
+import android.util.Log
 import kotlinx.datetime.DatePeriod
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.minus
@@ -30,6 +31,8 @@ import plus.rua.project.DayCellInfo
 import plus.rua.project.LunarCache
 import plus.rua.project.ShiftKind
 
+private const val TAG_CMP = "CalendarExpandAnim"
+
 
 /**
  * 月度日历网格页面，支持两阶段折叠动画。
@@ -185,7 +188,7 @@ private fun WeekRow(
             !hasAnchor -> weekIndex * h - collapseProgress * weeksSize * h
             isAnchor -> anchorIndex * h * (1f - phase1)
             isAbove -> weekIndex * h - phase1 * anchorIndex * h
-            isBelow -> weekIndex * h - phase1 * anchorIndex * h - phase2 * belowRowsHeight
+            isBelow -> weekIndex * h - phase1 * anchorIndex * h
             else -> weekIndex * h
         }
     } else 0f
@@ -198,6 +201,10 @@ private fun WeekRow(
         else -> 1f
     }
 
+    if (isAnchor || isBelow) {
+        Log.d(TAG_CMP, "WeekRow[$weekIndex]: isAnchor=$isAnchor isAbove=$isAbove isBelow=$isBelow phase1=$phase1 phase2=$phase2 yOffsetPx=$yOffsetPx rowAlpha=$rowAlpha collapseProgress=$collapseProgress")
+    }
+
     if (rowAlpha > 0.01f) {
         Row(
             modifier = Modifier

core/src/main/kotlin/plus/rua/project/ui/CalendarMonthView.kt

@@ -520,20 +520,66 @@ private fun CalendarPagerArea(
         modifier
     }
 
-    CalendarPager(
-        selectedDate = selectedDate,
-        today = today,
-        onDateClick = onDateClick,
-        onMonthChanged = onMonthChanged,
-        collapseProgress = collapseProgress,
-        rowHeightPx = rowHeightPx,
-        effectiveWeeks = effectiveWeeks,
-        shiftKindAt = shiftKindAt,
-        showLegalHoliday = showLegalHoliday,
-        onRowHeightMeasured = onRowHeightMeasured,
-        pagerState = pagerState,
+    // 延迟切换：等折叠 spring 动画完全稳定后再切到 WeekPager，避免视觉跳跃
+    var showWeekPager by remember { mutableStateOf(false) }
+
+    LaunchedEffect(isCollapsed, collapseProgress) {
+        if (isCollapsed && collapseProgress >= 0.999f) {
+            delay(50)
+            showWeekPager = true
+        } else if (!isCollapsed) {
+            showWeekPager = false
+        }
+    }
+
+    AnimatedContent(
+        targetState = showWeekPager,
+        transitionSpec = { fadeIn(tween(80)) togetherWith fadeOut(tween(80)) },
+        label = "pager_switch",
         modifier = pagerModifier
-    )
+    ) { useWeekPager ->
+        if (useWeekPager) {
+            WeekPager(
+                selectedDate = selectedDate,
+                today = today,
+                onDateClick = onDateClick,
+                onWeekChanged = { weekMonday ->
+                    val weekSunday = weekMonday.plus(DatePeriod(days = 6))
+                    val date = when {
+                        today in weekMonday..weekSunday -> today
+                        weekMonday.month != weekSunday.month -> {
+                            if (weekMonday < selectedDate) {
+                                @Suppress("DEPRECATION")
+                                LocalDate(weekSunday.year, weekSunday.month.number, 1)
+                            } else {
+                                weekMonday
+                            }
+                        }
+                        else -> weekMonday
+                    }
+                    onDateClick(date)
+                },
+                shiftKindAt = shiftKindAt,
+                showLegalHoliday = showLegalHoliday,
+                modifier = Modifier
+            )
+        } else {
+            CalendarPager(
+                selectedDate = selectedDate,
+                today = today,
+                onDateClick = onDateClick,
+                onMonthChanged = onMonthChanged,
+                collapseProgress = collapseProgress,
+                rowHeightPx = rowHeightPx,
+                effectiveWeeks = effectiveWeeks,
+                shiftKindAt = shiftKindAt,
+                showLegalHoliday = showLegalHoliday,
+                onRowHeightMeasured = onRowHeightMeasured,
+                pagerState = pagerState,
+                modifier = Modifier
+            )
+        }
+    }
 }
 
 @Composable

core/src/main/kotlin/plus/rua/project/ui/WeekPager.kt

@@ -18,10 +18,13 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.unit.dp
 import kotlinx.coroutines.flow.drop
+import kotlinx.coroutines.runBlocking
 import kotlinx.datetime.DatePeriod
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.daysUntil
 import kotlinx.datetime.plus
+import plus.rua.project.DayCellInfo
+import plus.rua.project.LunarCache
 import plus.rua.project.ShiftKind
 import plus.rua.project.composeTraceBeginSection
 import plus.rua.project.composeTraceEndSection
@@ -96,6 +99,11 @@ fun WeekPager(
         ) {
             (0 until 7).forEach { dayOffset ->
                 val date = weekMonday.plus(DatePeriod(days = dayOffset))
+                val lunarData = remember(date) {
+                    runBlocking {
+                        LunarCache.default.getOrCompute(date)
+                    }
+                }
                 DayCell(
                     date = date,
                     isCurrentMonth = date.month == selectedDate.month
@@ -106,7 +114,8 @@ fun WeekPager(
                     showLegalHoliday = showLegalHoliday,
                     onClick = { onDateClick(date) },
                     modifier = Modifier.weight(1f),
-                    interactionSource = interactionSource
+                    interactionSource = interactionSource,
+                    lunarData = lunarData
                 )
             }
         }