fix(reader): wire ReaderScreen to Episteme engine via MainViewModel

- ReaderScreen now gets MainViewModel from activity scope via viewModel()
- Calls viewModel.onFileSelected(uri) to trigger book import/open
- Renders EpubReaderScreen for EPUB/FB2/MOBI/etc, PdfViewerScreen for PDF
- Shows loading indicator while book is being imported
- Shows error message if import fails
- ':app:assembleOssDebug' passes, APK deployed.

app/src/main/java/org/dueattendant149/bookreader/ui/screens/reader/ReaderScreen.kt

@@ -4,17 +4,22 @@ import android.net.Uri
 import androidx.activity.compose.BackHandler
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.unit.sp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import org.dueattendant149.bookreader.MainViewModel
 
-/**
- * Placeholder reader screen — wraps the Episteme reader engine.
- * In production this delegates to EpubReaderScreen/PdfViewerScreen based on file type.
- */
+@OptIn(ExperimentalMaterial3Api::class)
 @Composable
 fun ReaderScreen(
     bookUri: String,
@@ -22,14 +27,76 @@ fun ReaderScreen(
 ) {
     BackHandler { onBackClick() }
 
-    Box(
-        modifier = Modifier.fillMaxSize(),
-        contentAlignment = Alignment.Center,
-    ) {
-        Text(
-            text = "Reader: $bookUri",
-            color = MaterialTheme.colorScheme.onBackground,
-            fontSize = 16.sp,
+    val context = LocalContext.current
+    val viewModel: MainViewModel = viewModel(
+        viewModelStoreOwner = context as androidx.lifecycle.ViewModelStoreOwner,
+    )
+
+    LaunchedEffect(bookUri) {
+        val uri = Uri.parse(bookUri)
+        viewModel.onFileSelected(uri, isFromRecent = false)
+    }
+
+    val uiState by viewModel.uiState.collectAsState()
+
+    val fileType = uiState.selectedFileType
+    val isPdf = fileType != null && fileType.name == "PDF"
+    val isEpub = fileType != null && fileType.name != "PDF"
+
+    Box(modifier = Modifier.fillMaxSize()) {
+        when {
+            uiState.isLoading -> {
+                CircularProgressIndicator(
+                    modifier = Modifier.align(Alignment.Center),
+                    color = MaterialTheme.colorScheme.primary,
                 )
             }
+            isEpub && uiState.selectedEpubBook != null -> {
+                org.dueattendant149.bookreader.epubreader.EpubReaderScreen(
+                    epubBook = uiState.selectedEpubBook!!,
+                    renderMode = uiState.renderMode,
+                    initialLocator = uiState.initialLocator,
+                    initialCfi = uiState.initialCfi,
+                    initialBookmarksJson = uiState.initialBookmarksJson,
+                    isProUser = uiState.isProUser,
+                    coverImagePath = null,
+                    onNavigateBack = { onBackClick() },
+                    onSavePosition = { _, _, _ -> },
+                    onBookmarksChanged = { },
+                    onNavigateToPro = { },
+                    onRenderModeChange = { },
+                    customFonts = emptyList(),
+                    onImportFonts = { },
+                    viewModel = viewModel,
+                )
+            }
+            isPdf && uiState.selectedPdfUri != null -> {
+                org.dueattendant149.bookreader.pdf.PdfViewerScreen(
+                    pdfUri = uiState.selectedPdfUri!!,
+                    initialPage = uiState.initialPageInBook,
+                    initialBookmarksJson = uiState.initialBookmarksJson,
+                    isProUser = uiState.isProUser,
+                    onNavigateBack = { onBackClick() },
+                    onSavePosition = { _, _ -> },
+                    onBookmarksChanged = { },
+                    onNavigateToPro = { },
+                    viewModel = viewModel,
+                )
+            }
+            uiState.errorMessage != null -> {
+                Text(
+                    text = uiState.errorMessage!!,
+                    color = MaterialTheme.colorScheme.error,
+                    fontSize = 16.sp,
+                    modifier = Modifier.align(Alignment.Center),
+                )
+            }
+            else -> {
+                CircularProgressIndicator(
+                    modifier = Modifier.align(Alignment.Center),
+                    color = MaterialTheme.colorScheme.primary,
+                )
+            }
+        }
+    }
 }