fix(sidebar): persist disclosure group state across hide/show cycles

Disclosure groups were losing their expanded/collapsed state when the sidebar
was hidden and shown again, because AnimatedVisibility removes them from
the composition tree, destroying local remember() state.

Now, Scaffold remembers a shared SnapshotStateMap above AnimatedVisibility
and provides it via LocalSidebarDisclosureStates. DisclosureItem reads/writes
from this map when available, falling back to local state when used standalone.

Author: kdroidFilter

macosui/src/commonMain/kotlin/io/github/kdroidfilter/nucleus/ui/apple/macos/components/Scaffold.kt

@@ -24,6 +24,7 @@ import androidx.compose.ui.draw.drawWithContent
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateMapOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
@@ -47,6 +48,7 @@ import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.LocalSidebarWidth
 import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.LocalTitleBarHeight
 import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.SidebarResizeCallbacks
 import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.LocalToolbarGlassState
+import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.LocalSidebarDisclosureStates
 import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.LocalSidebarHide
 import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.LocalSidebarVisible
 import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.macosSpring
@@ -171,6 +173,10 @@ fun Scaffold(
         Color.Transparent
     }
 
+    // Disclosure expanded states — remembered above AnimatedVisibility so they
+    // survive sidebar hide/show cycles.
+    val sidebarDisclosureStates = remember { mutableStateMapOf<String, Boolean>() }
+
     CompositionLocalProvider(LocalTitleBarHeight provides topPadding) {
 
         @Composable
@@ -214,6 +220,7 @@ fun Scaffold(
                         LocalSidebarResize provides sidebarResizeCallbacks,
                         LocalSidebarHide provides hideCallback,
                         LocalSidebarVisible provides showSidebar,
+                        LocalSidebarDisclosureStates provides sidebarDisclosureStates,
                     ) {
                         sidebar()
                     }

macosui/src/commonMain/kotlin/io/github/kdroidfilter/nucleus/ui/apple/macos/components/Sidebar.kt

@@ -48,6 +48,7 @@ import io.github.kdroidfilter.nucleus.ui.apple.macos.components.VerticalScrollba
 import io.github.kdroidfilter.nucleus.ui.apple.macos.components.TrackClickBehavior
 import io.github.kdroidfilter.nucleus.ui.apple.macos.components.rememberScrollbarState
 import io.github.kdroidfilter.nucleus.ui.apple.macos.components.Text
+import io.github.kdroidfilter.nucleus.ui.apple.macos.theme.LocalSidebarDisclosureStates
 import io.github.kdroidfilter.nucleus.ui.apple.macos.icons.Icons
 import io.github.kdroidfilter.nucleus.ui.apple.macos.icons.LucideChevronsLeft
 import io.github.kdroidfilter.nucleus.ui.apple.macos.icons.Icon
@@ -721,7 +722,16 @@ private fun DisclosureItem(
     itemColors: SidebarItemColors,
     indentLevel: Int = 0,
 ) {
-    var expanded by remember { mutableStateOf(item.initiallyExpanded) }
+    // When inside a Scaffold, use the shared map that survives AnimatedVisibility.
+    // Otherwise, fall back to local state.
+    val sharedStates = LocalSidebarDisclosureStates.current
+    var localExpanded by remember { mutableStateOf(item.initiallyExpanded) }
+    val expanded = sharedStates?.getOrPut(item.id) { item.initiallyExpanded } ?: localExpanded
+    val toggleExpanded = {
+        val newValue = !expanded
+        if (sharedStates != null) sharedStates[item.id] = newValue
+        localExpanded = newValue
+    }
     val chevronRotation by animateFloatAsState(
         targetValue = if (expanded) 90f else 0f,
         animationSpec = sidebarSpring(),
@@ -761,7 +771,7 @@ private fun DisclosureItem(
                 .clickable(
                     interactionSource = remember { MutableInteractionSource() },
                     indication = null,
-                ) { expanded = !expanded },
+                ) { toggleExpanded() },
             contentAlignment = Alignment.Center,
         ) {
             Icon(
@@ -777,7 +787,7 @@ private fun DisclosureItem(
             SidebarItemRow(
                 label = item.label,
                 onClick = {
-                    expanded = !expanded
+                    toggleExpanded()
                     item.onClick()
                 },
                 active = activeItem == item.id,

macosui/src/commonMain/kotlin/io/github/kdroidfilter/nucleus/ui/apple/macos/theme/Glass.kt

@@ -4,6 +4,7 @@ import androidx.compose.foundation.background
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.Immutable
 import androidx.compose.runtime.compositionLocalOf
+import androidx.compose.runtime.snapshots.SnapshotStateMap
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.draw.drawWithContent
@@ -74,6 +75,14 @@ val LocalSidebarHide = compositionLocalOf<(() -> Unit)?> { null }
  */
 val LocalSidebarVisible = compositionLocalOf { true }
 
+/**
+ * Stores the expanded/collapsed state of sidebar disclosure items by their ID.
+ * Provided by [Scaffold][io.github.kdroidfilter.nucleus.ui.apple.macos.components.Scaffold]
+ * above [AnimatedVisibility] so the state survives sidebar hide/show cycles.
+ * Null when no scaffold is providing state (disclosure items fall back to local remember).
+ */
+val LocalSidebarDisclosureStates = compositionLocalOf<SnapshotStateMap<String, Boolean>?> { null }
+
 /**
  * The two glass appearance variants matching macOS 26.
  *