fix(convert): simplify output names and harden writes

test/audio_conversion_utils_test.dart

@@ -47,20 +47,18 @@ void main() {
   });
 
   group('kept conversion output identity', () {
-    test('uses a distinct filename when the original is retained', () {
+    test('keeps the original base name and only changes the extension', () {
       expect(
         convertedOutputFileName(
           originalFileName: 'Track.flac',
           targetFormat: 'FLAC',
-          keepOriginal: true,
         ),
-        'Track_converted.flac',
+        'Track.flac',
       );
       expect(
         convertedOutputFileName(
           originalFileName: 'Track.flac',
           targetFormat: 'MP3',
-          keepOriginal: false,
         ),
         'Track.mp3',
       );

test/batch_track_actions_test.dart

@@ -0,0 +1,94 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:spotiflac_android/l10n/app_localizations.dart';
+import 'package:spotiflac_android/models/unified_library_item.dart';
+import 'package:spotiflac_android/services/batch_track_actions.dart';
+
+void main() {
+  testWidgets(
+    'batch conversion keeps a valid context after its launcher is removed',
+    (tester) async {
+      await tester.pumpWidget(
+        const ProviderScope(
+          child: MaterialApp(
+            localizationsDelegates: [
+              AppLocalizations.delegate,
+              GlobalMaterialLocalizations.delegate,
+              GlobalWidgetsLocalizations.delegate,
+              GlobalCupertinoLocalizations.delegate,
+            ],
+            supportedLocales: AppLocalizations.supportedLocales,
+            home: _BatchConvertHarness(),
+          ),
+        ),
+      );
+
+      await tester.tap(find.byKey(const Key('open-batch-convert')));
+      await tester.pumpAndSettle();
+
+      final convertButton = find.widgetWithText(
+        FilledButton,
+        'Convert 1 track',
+      );
+      await tester.scrollUntilVisible(
+        convertButton,
+        300,
+        scrollable: find.byType(Scrollable).last,
+      );
+      await tester.tap(convertButton);
+      await tester.pumpAndSettle();
+
+      expect(find.byType(AlertDialog), findsOneWidget);
+      expect(
+        find.textContaining('Original files will be deleted'),
+        findsOneWidget,
+      );
+      expect(tester.takeException(), isNull);
+    },
+  );
+}
+
+class _BatchConvertHarness extends ConsumerStatefulWidget {
+  const _BatchConvertHarness();
+
+  @override
+  ConsumerState<_BatchConvertHarness> createState() =>
+      _BatchConvertHarnessState();
+}
+
+class _BatchConvertHarnessState extends ConsumerState<_BatchConvertHarness> {
+  bool _showLauncher = true;
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: _showLauncher
+          ? Builder(
+              builder: (launcherContext) => FilledButton(
+                key: const Key('open-batch-convert'),
+                onPressed: () => showBatchConvertSheet(
+                  launcherContext,
+                  ref,
+                  [
+                    UnifiedLibraryItem(
+                      id: 'track-1',
+                      trackName: 'Track',
+                      artistName: 'Artist',
+                      albumName: 'Album',
+                      filePath: '/music/track.flac',
+                      addedAt: DateTime(2026),
+                      source: LibraryItemSource.local,
+                    ),
+                  ],
+                  onExitSelectionMode: () {},
+                  onSheetOpen: () => setState(() => _showLauncher = false),
+                ),
+                child: const Text('Open'),
+              ),
+            )
+          : const SizedBox.shrink(),
+    );
+  }
+}

test/conversion_library_service_test.dart

@@ -0,0 +1,70 @@
+import 'dart:convert';
+
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:spotiflac_android/services/conversion_library_service.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+  const channel = MethodChannel('com.zarz.spotiflac/backend');
+
+  tearDown(() async {
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+        .setMockMethodCallHandler(channel, null);
+  });
+
+  test(
+    'SAF conversion removes _converted and retries a transient write',
+    () async {
+      var attempts = 0;
+      TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+          .setMockMethodCallHandler(channel, (call) async {
+            expect(call.method, 'safCreateUniqueFromPath');
+            expect((call.arguments as Map)['file_name'], 'Song.mp3');
+            attempts++;
+            if (attempts == 1) {
+              throw PlatformException(code: 'temporary_io');
+            }
+            return jsonEncode({
+              'uri': 'content://music/Song%20(2).mp3',
+              'file_name': 'Song (2).mp3',
+            });
+          });
+
+      final published = await ConversionLibraryService.publishSafConversion(
+        treeUri: 'content://music/tree/root',
+        relativeDir: 'Album',
+        originalFileName: 'Song.flac',
+        targetFormat: 'mp3',
+        sourcePath: '/tmp/Song.mp3',
+        keepOriginal: true,
+      );
+
+      expect(attempts, 2);
+      expect(published?.fileName, 'Song (2).mp3');
+    },
+  );
+
+  test(
+    'same-format replacement reuses the original SAF document name',
+    () async {
+      TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+          .setMockMethodCallHandler(channel, (call) async {
+            expect(call.method, 'safCreateFromPath');
+            expect((call.arguments as Map)['file_name'], 'Song.flac');
+            return 'content://music/Song.flac';
+          });
+
+      final published = await ConversionLibraryService.publishSafConversion(
+        treeUri: 'content://music/tree/root',
+        relativeDir: 'Album',
+        originalFileName: 'Song.flac',
+        targetFormat: 'flac',
+        sourcePath: '/tmp/Song.flac',
+        keepOriginal: false,
+      );
+
+      expect(published?.fileName, 'Song.flac');
+    },
+  );
+}