feat(build): KMP → Android-only migration (Phase 1.2)

- Delete desktopApp/ and shared/ modules.
- Merge shared commonMain + androidMain + readerJvmMain sources into app/src/main/kotlin.
- Resolve expect/actual declarations by keeping android implementations.
- Remove project(':shared') dependency and KMP plugins from build files.
- Simplify settings.gradle.kts to single :app module; root project renamed BookReader.
- Remove JVM-only code (javax.imageio/ImageIO in SharedJvmBookLoader).
- Make LocalFolderSync helpers public for cross-package use in Android module.
- Baseline ':app:assembleOssDebug' passes (APK ~80 MB).

app/build.gradle.kts

@@ -217,8 +217,6 @@ kover {
 //noinspection UseTomlInstead
 dependencies {
 
-    implementation(project(":shared"))
-
     implementation(libs.androidx.core.ktx)
     implementation(libs.androidx.lifecycle.runtime.ktx)
     implementation(libs.androidx.activity.compose)

app/src/main/kotlin/com/dueattendant149/bookreader/reader/shared/LibraryProjector.kt

@@ -160,8 +160,6 @@ private fun ImportedFile.toImportedBookFile(): ImportedBookFile {
     )
 }
 
-expect fun currentTimestamp(): Long
-
 fun String.toFileType(): FileType {
     return SharedFileCapabilities.fileTypeForName(this)
 }

app/src/main/kotlin/com/dueattendant149/bookreader/reader/shared/LocalFolderSync.kt

@@ -19,7 +19,10 @@ const val LOCAL_FOLDER_SYNC_DATA_DIR = "EpistemeSyncData"
 const val LOCAL_FOLDER_ANNOTATION_SUFFIX = "_annotations"
 const val LOCAL_FOLDER_SIDECAR_HASH_PREFIX = "book_"
 
-internal expect fun localFolderSyncSha256ShortHex(value: String): String
+fun localFolderSyncSha256ShortHex(value: String): String {
+    val bytes = java.security.MessageDigest.getInstance("SHA-256").digest(value.toByteArray())
+    return bytes.joinToString("") { "%02x".format(it) }.take(12)
+}
 
 fun localFolderSyncSidecarStem(bookId: String): String {
     return LOCAL_FOLDER_SIDECAR_HASH_PREFIX + localFolderSyncSha256ShortHex(bookId)

app/src/main/kotlin/com/dueattendant149/bookreader/reader/shared/Platform.kt

@@ -0,0 +1,3 @@
+package org.dueattendant149.bookreader.shared
+
+fun currentTimestamp(): Long = System.currentTimeMillis()

app/src/main/kotlin/com/dueattendant149/bookreader/reader/shared/reader/SharedReaderDiagnostics.kt

@@ -0,0 +1,27 @@
+package org.dueattendant149.bookreader.shared.reader
+
+import android.util.Log
+import org.dueattendant149.bookreader.BuildConfig
+
+const val SharedReaderDiagnosticsProperty = "episteme.desktop.diagnostics"
+const val SharedReaderDiagnosticsTagsProperty = "episteme.desktop.diagnostics.tags"
+const val SharedEpubCutoffDiagnosticsTag = "EpistemeEpubCutoff"
+
+val SharedReaderDiagnosticsEnabled: Boolean = BuildConfig.DEBUG
+
+fun isSharedReaderDiagnosticTagEnabled(tag: String): Boolean {
+    if (!BuildConfig.DEBUG) return false
+    return tag == SharedEpubCutoffDiagnosticsTag ||
+        runCatching { Log.isLoggable(tag, Log.DEBUG) }.getOrDefault(false)
+}
+
+fun writeSharedReaderDiagnostic(tag: String, message: String) {
+    if (!BuildConfig.DEBUG) return
+    Log.d(tag, message)
+}
+
+inline fun logSharedReaderDiagnostic(tag: String, message: () -> String) {
+    if (SharedReaderDiagnosticsEnabled && isSharedReaderDiagnosticTagEnabled(tag)) {
+        writeSharedReaderDiagnostic(tag, message())
+    }
+}

app/src/main/kotlin/com/dueattendant149/bookreader/reader/shared/ui/LocalBookCoverImage.kt

@@ -9,7 +9,7 @@ import androidx.compose.ui.graphics.asImageBitmap
 import androidx.compose.ui.layout.ContentScale
 
 @Composable
-internal actual fun LocalBookCoverImage(
+internal fun LocalBookCoverImage(
     path: String,
     contentDescription: String?,
     modifier: Modifier

app/src/main/kotlin/com/dueattendant149/bookreader/reader/shared/ui/SharedReaderModalLayer.kt

@@ -2,6 +2,8 @@ package org.dueattendant149.bookreader.shared.ui
 
 import androidx.compose.runtime.compositionLocalOf
 import androidx.compose.runtime.Composable
+import androidx.compose.ui.window.Dialog
+import androidx.compose.ui.window.DialogProperties
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 
@@ -40,20 +42,32 @@ fun sharedReaderPopupWidth(
     return (availableWidth * widthFraction.coerceIn(0f, 1f)).coerceIn(lowerBound, upperBound)
 }
 
+
 @Composable
-internal expect fun SharedReaderModalLayer(
+internal fun SharedReaderModalLayer(
     onDismiss: () -> Unit,
     level: SharedReaderModalLevel = SharedReaderModalLevel.Popup,
     content: @Composable () -> Unit
-)
+) {
+    Dialog(
+        onDismissRequest = onDismiss,
+        properties = DialogProperties(usePlatformDefaultWidth = false)
+    ) {
+        content()
+    }
+}
 
-internal expect fun sharedReaderModalLayerUsesSizedEdgeWindow(level: SharedReaderModalLevel): Boolean
+internal fun sharedReaderModalLayerUsesSizedEdgeWindow(level: SharedReaderModalLevel): Boolean {
+    return false
+}
 
 @Composable
-expect fun SharedReaderModalOwnerWindowProvider(
+fun SharedReaderModalOwnerWindowProvider(
     ownerWindow: Any?,
     content: @Composable () -> Unit
-)
+) {
+    content()
+}
 
 @Composable
 fun SharedReaderPopupLayer(