Fix: extract FolderSection/GridItem to GridModels.kt, make FolderDividerHeader internal

FolderSection was private in BrowseScreen.kt, blocking DensePhotoGrid
from using it. Moved to GridModels.kt along with GridItemType and GridItem.
FolderDividerHeader made internal so both grid views can share it.

src/main/kotlin/com/bolenpad/photophetch/ui/BrowseScreen.kt

@@ -191,12 +191,6 @@ fun BrowseScreen(state: AppState) {
 
 // ─── Data helpers ──────────────────────────────────────────────────────────────
 
-private data class FolderSection(
-    val folder: FolderInfo,
-    val byDay: List<Pair<java.time.LocalDate, List<PhonePhoto>>>,
-    val allPhotos: List<PhonePhoto>,
-)
-
 private fun buildFolderSections(pl: PhotoListState.Loaded): List<FolderSection> {
     val zoneId = java.time.ZoneId.systemDefault()
     return pl.folders.map { folder ->
@@ -400,7 +394,7 @@ private fun UnifiedPhotoScroll(
 }
 
 @Composable
-private fun FolderDividerHeader(
+internal fun FolderDividerHeader(
     name: String,
     total: Int,
     selected: Int,

src/main/kotlin/com/bolenpad/photophetch/ui/DensePhotoGrid.kt

@@ -47,7 +47,7 @@ import java.time.format.DateTimeFormatter
  */
 @Composable
 fun DensePhotoGrid(
-    folderSections: List<com.bolenpad.photophetch.ui.FolderSection>,
+    folderSections: List<FolderSection>,
     selectedPhotos: Set<PhonePhoto>,
     device: DeviceInfo?,
     adbBin: String,
@@ -69,13 +69,6 @@ fun DensePhotoGrid(
     val scope = rememberCoroutineScope()
 
     // Build flat item list: folder header + photo rows per section
-    data class GridItem(
-        val type: GridItemType,
-        val folderSection: com.bolenpad.photophetch.ui.FolderSection? = null,
-        val rowPhotos: List<PhonePhoto>? = null,
-    )
-    enum class GridItemType { FOLDER_HEADER, PHOTO_ROW }
-
     val items: List<GridItem> = buildList {
         folderSections.forEach { section ->
             if (section.allPhotos.isEmpty()) return@forEach

src/main/kotlin/com/bolenpad/photophetch/ui/GridModels.kt

@@ -0,0 +1,21 @@
+package com.bolenpad.photophetch.ui
+
+import com.bolenpad.photophetch.model.PhonePhoto
+import java.time.LocalDate
+
+/** A folder's photos grouped by day, used by both Grouped and Dense grid views */
+data class FolderSection(
+    val folder: FolderInfo,
+    val byDay: List<Pair<LocalDate, List<PhonePhoto>>>,
+    val allPhotos: List<PhonePhoto>,
+)
+
+/** Item types used in the DensePhotoGrid flat list */
+enum class GridItemType { FOLDER_HEADER, PHOTO_ROW }
+
+/** A single item in the DensePhotoGrid flat list */
+data class GridItem(
+    val type: GridItemType,
+    val folderSection: FolderSection? = null,
+    val rowPhotos: List<PhonePhoto>? = null,
+)