Add close button and swipe-left-to-close on view all pages

- X button in top app bar navigates back to notebook list
- Swipe left gesture (>200px) on the page grid closes to notebook list
- Both clear the notebook and view-all-pages state in SharedPreferences

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

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

@@ -159,6 +159,11 @@ fun EngPadNavGraph(
                             ?.set("selectedPageId", pageId)
                         navController.popBackStack()
                     },
+                    onClose = {
+                        onNotebookClosed()
+                        onViewAllPagesChanged(false)
+                        navController.popBackStack(Routes.NOTEBOOKS, false)
+                    },
                 )
             }
         }

app/src/main/kotlin/net/metacircular/engpad/ui/pages/PageListScreen.kt

@@ -4,6 +4,7 @@ import android.graphics.Paint as AndroidPaint
 import android.graphics.Path as AndroidPath
 import androidx.compose.foundation.Canvas
 import androidx.compose.foundation.clickable
+import androidx.compose.foundation.gestures.detectHorizontalDragGestures
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -39,6 +40,7 @@ import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.graphics.nativeCanvas
@@ -65,6 +67,7 @@ fun PageListScreen(
     pageSize: PageSize,
     database: EngPadDatabase,
     onPageClick: (Long, PageSize) -> Unit,
+    onClose: () -> Unit,
 ) {
     val repository = remember {
         PageRepository(database.pageDao(), database.strokeDao())
@@ -97,7 +100,14 @@ fun PageListScreen(
 
     Scaffold(
         topBar = {
-            TopAppBar(title = { Text(notebookTitle) })
+            TopAppBar(
+                title = { Text(notebookTitle) },
+                navigationIcon = {
+                    androidx.compose.material3.IconButton(onClick = onClose) {
+                        Text("X")
+                    }
+                },
+            )
         },
         floatingActionButton = {
             FloatingActionButton(onClick = { viewModel.addPage() }) {
@@ -105,11 +115,31 @@ fun PageListScreen(
             }
         },
     ) { padding ->
+        // Detect left swipe from right edge to close
+        var swipeCumulative by remember { mutableStateOf(0f) }
+        val swipeModifier = Modifier.pointerInput(Unit) {
+            detectHorizontalDragGestures(
+                onDragStart = { startOffset ->
+                    swipeCumulative = 0f
+                },
+                onDragEnd = {
+                    if (swipeCumulative < -200f) { // Swipe left threshold
+                        onClose()
+                    }
+                    swipeCumulative = 0f
+                },
+                onHorizontalDrag = { _, dragAmount ->
+                    swipeCumulative += dragAmount
+                },
+            )
+        }
+
         if (pages.isEmpty()) {
             Column(
                 modifier = Modifier
                     .fillMaxSize()
-                    .padding(padding),
+                    .padding(padding)
+                    .then(swipeModifier),
                 verticalArrangement = Arrangement.Center,
                 horizontalAlignment = Alignment.CenterHorizontally,
             ) {
@@ -121,7 +151,8 @@ fun PageListScreen(
                 modifier = Modifier
                     .fillMaxSize()
                     .padding(padding)
-                    .padding(8.dp),
+                    .padding(8.dp)
+                    .then(swipeModifier),
                 state = lazyGridState,
                 horizontalArrangement = Arrangement.spacedBy(8.dp),
                 verticalArrangement = Arrangement.spacedBy(8.dp),