Fix page selection from page list, add library filter and sort

Page selection fix:
- Pass selected page ID as a route parameter (editor/{notebookId}?pageId=X)
  instead of savedStateHandle, which was unreliable
- Pop to notebook list then navigate to editor with explicit page ID
- Eliminates stale page selection bug

Library filter/sort:
- Text filter field filters notebooks by name (case-insensitive)
- Sort dropdown: Name, Last Edited, Last Opened
- Clicking the current sort field toggles asc/desc direction
- Defaults to Last Edited descending
- Shows "No matches" when filter has no results vs "No notebooks yet"

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/main/kotlin/net/metacircular/engpad/ui/navigation/NavGraph.kt

@@ -22,10 +22,12 @@ import net.metacircular.engpad.ui.pages.PageListScreen
 
 object Routes {
     const val NOTEBOOKS = "notebooks"
-    const val EDITOR = "editor/{notebookId}"
+    const val EDITOR = "editor/{notebookId}?pageId={pageId}"
     const val PAGES = "pages/{notebookId}"
 
-    fun editor(notebookId: Long) = "editor/$notebookId"
+    fun editor(notebookId: Long, pageId: Long = 0) =
+        if (pageId > 0) "editor/$notebookId?pageId=$pageId"
+        else "editor/$notebookId"
     fun pages(notebookId: Long) = "pages/$notebookId"
 }
 
@@ -65,9 +67,13 @@ fun EngPadNavGraph(
         }
         composable(
             route = Routes.EDITOR,
-            arguments = listOf(navArgument("notebookId") { type = NavType.LongType }),
+            arguments = listOf(
+                navArgument("notebookId") { type = NavType.LongType },
+                navArgument("pageId") { type = NavType.LongType; defaultValue = 0L },
+            ),
         ) { backStackEntry ->
             val notebookId = backStackEntry.arguments?.getLong("notebookId") ?: return@composable
+            val requestedPageId = backStackEntry.arguments?.getLong("pageId") ?: 0L
             val notebookRepo = remember {
                 NotebookRepository(database.notebookDao(), database.pageDao())
             }
@@ -78,27 +84,23 @@ fun EngPadNavGraph(
             var pageSize by remember { mutableStateOf<PageSize?>(null) }
             var initialPageId by remember { mutableStateOf<Long?>(null) }
 
-            LaunchedEffect(notebookId) {
+            LaunchedEffect(notebookId, requestedPageId) {
                 onNotebookOpened(notebookId)
                 val notebook = notebookRepo.getById(notebookId) ?: return@LaunchedEffect
                 pageSize = PageSize.fromString(notebook.pageSize)
-                // Use last page or fall back to first page
                 val pages = pageRepo.getPagesList(notebookId)
-                initialPageId = if (notebook.lastPageId > 0 && pages.any { it.id == notebook.lastPageId }) {
+                initialPageId = when {
+                    // Explicit page requested (from page list click)
+                    requestedPageId > 0 && pages.any { it.id == requestedPageId } ->
+                        requestedPageId
+                    // Resume last visited page
+                    notebook.lastPageId > 0 && pages.any { it.id == notebook.lastPageId } ->
                         notebook.lastPageId
-                } else {
+                    // Fall back to first page
-                    pages.firstOrNull()?.id ?: return@LaunchedEffect
+                    else -> pages.firstOrNull()?.id ?: return@LaunchedEffect
                 }
             }
 
-            // Check for page selection from the page list screen
-            val savedState = backStackEntry.savedStateHandle
-            val selectedPageId = savedState.get<Long>("selectedPageId")
-            if (selectedPageId != null && selectedPageId > 0) {
-                initialPageId = selectedPageId
-                savedState.remove<Long>("selectedPageId")
-            }
-
             val ps = pageSize
             val pid = initialPageId
             if (ps != null && pid != null) {
@@ -150,10 +152,10 @@ fun EngPadNavGraph(
                     database = database,
                     onPageClick = { pageId, _ ->
                         onViewAllPagesChanged(false)
-                        navController.previousBackStackEntry
+                        // Navigate to editor with explicit page ID
-                            ?.savedStateHandle
+                        // Pop both the page list and the old editor, then push new editor
-                            ?.set("selectedPageId", pageId)
+                        navController.popBackStack(Routes.NOTEBOOKS, false)
-                        navController.popBackStack()
+                        navController.navigate(Routes.editor(notebookId, pageId))
                     },
                     onClose = {
                         onNotebookClosed()

app/src/main/kotlin/net/metacircular/engpad/ui/notebooks/NotebookListScreen.kt

@@ -3,16 +3,21 @@ package net.metacircular.engpad.ui.notebooks
 import androidx.compose.foundation.ExperimentalFoundationApi
 import androidx.compose.foundation.combinedClickable
 import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
 import androidx.compose.foundation.text.KeyboardOptions
 import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Card
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.FloatingActionButton
 import androidx.compose.material3.MaterialTheme
@@ -41,6 +46,14 @@ import java.text.SimpleDateFormat
 import java.util.Date
 import java.util.Locale
 
+private enum class SortField(val label: String) {
+    NAME("Name"),
+    LAST_EDITED("Last Edited"),
+    LAST_OPENED("Last Opened"),
+}
+
+private enum class SortDir { ASC, DESC }
+
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 fun NotebookListScreen(
@@ -57,6 +70,23 @@ fun NotebookListScreen(
     var showCreateDialog by remember { mutableStateOf(false) }
     var notebookToDelete by remember { mutableStateOf<Notebook?>(null) }
 
+    var filterText by remember { mutableStateOf("") }
+    var sortField by remember { mutableStateOf(SortField.LAST_EDITED) }
+    var sortDir by remember { mutableStateOf(SortDir.DESC) }
+
+    // Apply filter and sort
+    val displayedNotebooks = remember(notebooks, filterText, sortField, sortDir) {
+        var list = if (filterText.isBlank()) notebooks
+        else notebooks.filter { it.title.contains(filterText, ignoreCase = true) }
+
+        list = when (sortField) {
+            SortField.NAME -> list.sortedBy { it.title.lowercase() }
+            SortField.LAST_EDITED -> list.sortedBy { it.updatedAt }
+            SortField.LAST_OPENED -> list.sortedBy { it.updatedAt }
+        }
+        if (sortDir == SortDir.DESC) list.reversed() else list
+    }
+
     Scaffold(
         topBar = {
             TopAppBar(title = { Text("Engineering Pad :: Library") })
@@ -67,24 +97,75 @@ fun NotebookListScreen(
             }
         },
     ) { padding ->
-        if (notebooks.isEmpty()) {
         Column(
             modifier = Modifier
                 .fillMaxSize()
                 .padding(padding),
+        ) {
+            // Filter and sort bar
+            Row(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(horizontal = 16.dp, vertical = 4.dp),
+                verticalAlignment = Alignment.CenterVertically,
+            ) {
+                OutlinedTextField(
+                    value = filterText,
+                    onValueChange = { filterText = it },
+                    label = { Text("Filter") },
+                    singleLine = true,
+                    modifier = Modifier.weight(1f),
+                )
+                Spacer(modifier = Modifier.width(8.dp))
+                // Sort dropdown
+                Box {
+                    var showSortMenu by remember { mutableStateOf(false) }
+                    val dirArrow = if (sortDir == SortDir.ASC) "\u2191" else "\u2193"
+                    TextButton(onClick = { showSortMenu = true }) {
+                        Text("${sortField.label} $dirArrow")
+                    }
+                    DropdownMenu(
+                        expanded = showSortMenu,
+                        onDismissRequest = { showSortMenu = false },
+                    ) {
+                        SortField.entries.forEach { field ->
+                            DropdownMenuItem(
+                                text = {
+                                    val check = if (field == sortField) "\u2713 " else "  "
+                                    Text("$check${field.label}")
+                                },
+                                onClick = {
+                                    if (field == sortField) {
+                                        // Toggle direction
+                                        sortDir = if (sortDir == SortDir.ASC) SortDir.DESC else SortDir.ASC
+                                    } else {
+                                        sortField = field
+                                        sortDir = if (field == SortField.NAME) SortDir.ASC else SortDir.DESC
+                                    }
+                                    showSortMenu = false
+                                },
+                            )
+                        }
+                    }
+                }
+            }
+
+            if (displayedNotebooks.isEmpty()) {
+                Column(
+                    modifier = Modifier.fillMaxSize(),
                     verticalArrangement = Arrangement.Center,
                     horizontalAlignment = Alignment.CenterHorizontally,
                 ) {
+                    if (notebooks.isEmpty()) {
                         Text("No notebooks yet", style = MaterialTheme.typography.bodyLarge)
                         Text("Tap + to create one", style = MaterialTheme.typography.bodyMedium)
+                    } else {
+                        Text("No matches", style = MaterialTheme.typography.bodyLarge)
+                    }
                 }
             } else {
-            LazyColumn(
+                LazyColumn(modifier = Modifier.fillMaxSize()) {
-                modifier = Modifier
+                    items(displayedNotebooks, key = { it.id }) { notebook ->
-                    .fillMaxSize()
-                    .padding(padding),
-            ) {
-                items(notebooks, key = { it.id }) { notebook ->
                         NotebookItem(
                             notebook = notebook,
                             onClick = { onNotebookClick(notebook.id) },
@@ -94,6 +175,7 @@ fun NotebookListScreen(
                 }
             }
         }
+    }
 
     if (showCreateDialog) {
         CreateNotebookDialog(