perf: 聚合 CalendarUiState 减少 Compose 重组

- ViewModel 新增 CalendarUiState 数据类，通过 combine + stateIn
  将 6 个独立 StateFlow 合并为单一 uiState 流
- CalendarMonthView 从 5 个分散 collectAsState 改为单个
  uiState.collectAsState，减少重组次数
- CalendarPagerArea 改为显式传参，解耦对 ViewModel 的直接引用
- CalendarMonthPage 中 DayCell 外层包裹 key(dayData.date)，
  稳定跨帧重组

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

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

@@ -4,8 +4,11 @@ import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.stateIn
 import kotlinx.datetime.DatePeriod
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.TimeZone
@@ -34,6 +37,21 @@ data class CalendarDay(
     val isSelected: Boolean
 )
 
+/**
+ * 日历 UI 状态聚合，用于减少 Compose 重组次数。
+ *
+ * 将多个独立的 StateFlow 合并为单一状态流，
+ * 避免 `collectAsState()` 分散订阅导致的重复重组。
+ */
+data class CalendarUiState(
+    val selectedDate: LocalDate,
+    val isCollapsed: Boolean,
+    val isYearView: Boolean,
+    val yearViewYear: Int,
+    val collapseProgress: Float,
+    val showLegalHoliday: Boolean
+)
+
 /**
  * 日历状态管理，持有选中日期、折叠状态和 ISO 周号计算逻辑。
  *
@@ -118,6 +136,26 @@ class CalendarViewModel(
     private val _showLegalHoliday = MutableStateFlow(false)
     val showLegalHoliday: StateFlow<Boolean> = _showLegalHoliday.asStateFlow()
 
+    /** 聚合 UI 状态，减少 Compose 层分散订阅导致的重组。 */
+    val uiState: StateFlow<CalendarUiState> = combine(
+        combine(_selectedDate, _isCollapsed, ::Pair),
+        combine(_isYearView, _yearViewYear, ::Pair),
+        combine(_collapseProgress, _showLegalHoliday, ::Pair)
+    ) { dateCollapsed, yearViewYearPair, progressHoliday ->
+        CalendarUiState(
+            selectedDate = dateCollapsed.first,
+            isCollapsed = dateCollapsed.second,
+            isYearView = yearViewYearPair.first,
+            yearViewYear = yearViewYearPair.second,
+            collapseProgress = progressHoliday.first,
+            showLegalHoliday = progressHoliday.second
+        )
+    }.stateIn(
+        viewModelScope,
+        SharingStarted.WhileSubscribed(5000),
+        CalendarUiState(today, false, false, today.year, 0f, false)
+    )
+
     /**
      * 选中指定日期。
      *

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

@@ -189,17 +189,19 @@ private fun WeekRow(
                 .padding(vertical = ROW_PADDING_DP.dp)
         ) {
             week.forEach { dayData ->
-                DayCell(
-                    date = dayData.date,
-                    isCurrentMonth = dayData.isCurrentMonth,
-                    isSelected = dayData.date == selectedDate,
-                    isToday = dayData.date == today,
-                    shiftKind = shiftKindAt(dayData.date),
-                    showLegalHoliday = showLegalHoliday,
-                    onClick = { onDateClick(dayData.date) },
-                    modifier = Modifier.weight(1f),
-                    interactionSource = interactionSource
-                )
+                key(dayData.date) {
+                    DayCell(
+                        date = dayData.date,
+                        isCurrentMonth = dayData.isCurrentMonth,
+                        isSelected = dayData.date == selectedDate,
+                        isToday = dayData.date == today,
+                        shiftKind = shiftKindAt(dayData.date),
+                        showLegalHoliday = showLegalHoliday,
+                        onClick = { onDateClick(dayData.date) },
+                        modifier = Modifier.weight(1f),
+                        interactionSource = interactionSource
+                    )
+                }
             }
         }
     }

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

@@ -72,6 +72,7 @@ import kotlinx.datetime.number
 import kotlinx.datetime.plus
 import kotlinx.datetime.todayIn
 import plus.rua.project.CalendarViewModel
+import plus.rua.project.ShiftKind
 import plus.rua.project.composeTraceBeginSection
 import plus.rua.project.composeTraceEndSection
 import kotlin.math.abs
@@ -95,15 +96,16 @@ fun CalendarMonthView(
     val viewModel = viewModel<CalendarViewModel>()
     val today = remember { Clock.System.todayIn(TimeZone.currentSystemDefault()) }
 
-    val selectedDate by viewModel.selectedDate.collectAsState()
+    val uiState by viewModel.uiState.collectAsState()
+    val selectedDate = uiState.selectedDate
     val currentYear = selectedDate.year
     @Suppress("DEPRECATION") // monthNumber 无替代 API，kotlinx-datetime 尚未提供新接口
     val currentMonth = selectedDate.month.number
-    val isCollapsed by viewModel.isCollapsed.collectAsState()
-    val isYearView by viewModel.isYearView.collectAsState()
-    val yearViewYear by viewModel.yearViewYear.collectAsState()
-    val collapseProgress by viewModel.collapseProgress.collectAsState()
-    val showLegalHoliday by viewModel.showLegalHoliday.collectAsState()
+    val isCollapsed = uiState.isCollapsed
+    val isYearView = uiState.isYearView
+    val yearViewYear = uiState.yearViewYear
+    val collapseProgress = uiState.collapseProgress
+    val showLegalHoliday = uiState.showLegalHoliday
 
     val density = LocalDensity.current
     val coroutineScope = rememberCoroutineScope()
@@ -210,10 +212,21 @@ fun CalendarMonthView(
                             )
                             with(sharedScope) {
                                 CalendarPagerArea(
-                                    viewModel = viewModel,
+                                    selectedDate = selectedDate,
                                     today = today,
+                                    isCollapsed = isCollapsed,
+                                    collapseProgress = collapseProgress,
+                                    showLegalHoliday = showLegalHoliday,
                                     rowHeightPx = rowHeightPx,
                                     screenWidthPx = screenWidthPx,
+                                    onDateClick = { date -> viewModel.selectDate(date) },
+                                    onMonthChanged = { year, month ->
+                                        @Suppress("DEPRECATION")
+                                        val date = if (year == today.year && today.month.number == month) today
+                                            else LocalDate(year, month, 1)
+                                        viewModel.selectDate(date)
+                                    },
+                                    shiftKindAt = { date -> viewModel.shiftKindAt(date) },
                                     onRowHeightMeasured = { h ->
                                         if (h > 0) rowHeightPx = h
                                     },
@@ -408,19 +421,21 @@ private fun MenuIcon(color: Color, modifier: Modifier = Modifier) {
 
 @Composable
 private fun CalendarPagerArea(
-    viewModel: CalendarViewModel,
+    selectedDate: LocalDate,
     today: LocalDate,
+    isCollapsed: Boolean,
+    collapseProgress: Float,
+    showLegalHoliday: Boolean,
     rowHeightPx: Int,
     screenWidthPx: Int,
+    onDateClick: (LocalDate) -> Unit,
+    onMonthChanged: (year: Int, month: Int) -> Unit,
+    shiftKindAt: (LocalDate) -> ShiftKind?,
     onRowHeightMeasured: ((Int) -> Unit)?,
     pagerState: PagerState,
     modifier: Modifier = Modifier
 ) {
     val density = LocalDensity.current
-    val collapseProgress by viewModel.collapseProgress.collectAsState()
-    val selectedDate by viewModel.selectedDate.collectAsState()
-    val isCollapsed by viewModel.isCollapsed.collectAsState()
-    val showLegalHoliday by viewModel.showLegalHoliday.collectAsState()
 
     val interpolatedWeeks by remember {
         derivedStateOf {
@@ -469,7 +484,7 @@ private fun CalendarPagerArea(
         WeekPager(
             selectedDate = selectedDate,
             today = today,
-            onDateClick = { date -> viewModel.selectDate(date) },
+            onDateClick = onDateClick,
             onWeekChanged = { weekMonday ->
                 val weekSunday = weekMonday.plus(DatePeriod(days = 6))
                 val date = when {
@@ -485,9 +500,9 @@ private fun CalendarPagerArea(
 
                     else -> weekMonday
                 }
-                viewModel.selectDate(date)
+                onDateClick(date)
             },
-            shiftKindAt = { date -> viewModel.shiftKindAt(date) },
+            shiftKindAt = shiftKindAt,
             showLegalHoliday = showLegalHoliday,
             modifier = pagerModifier
         )
@@ -495,18 +510,12 @@ private fun CalendarPagerArea(
         CalendarPager(
             selectedDate = selectedDate,
             today = today,
-            onDateClick = { date -> viewModel.selectDate(date) },
-            onMonthChanged = { year, month ->
-                @Suppress("DEPRECATION") // monthNumber 无替代 API
-                val date =
-                    if (year == today.year && today.month.number == month) today
-                    else LocalDate(year, month, 1)
-                viewModel.selectDate(date)
-            },
+            onDateClick = onDateClick,
+            onMonthChanged = onMonthChanged,
             collapseProgress = collapseProgress,
             rowHeightPx = rowHeightPx,
             effectiveWeeks = effectiveWeeks,
-            shiftKindAt = { date -> viewModel.shiftKindAt(date) },
+            shiftKindAt = shiftKindAt,
             showLegalHoliday = showLegalHoliday,
             onRowHeightMeasured = onRowHeightMeasured,
             pagerState = pagerState,