feat: save raw email to temp dir and add Share action to SnackBar (#115)

Save the .eml file to the temporary directory (reliable on all
platforms) and display a Share action in the SnackBar so users can
send the file to any app — including the Files app — which properly
registers it with Android's MediaStore and makes it visible in the
recently-used list.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/ui/screens/email_detail_screen.dart

@@ -9,6 +9,7 @@ import 'package:go_router/go_router.dart';
 import 'package:intl/intl.dart';
 import 'package:open_filex/open_filex.dart';
 import 'package:path_provider/path_provider.dart';
+import 'package:share_plus/share_plus.dart';
 
 import 'package:sharedinbox/core/models/email.dart';
 import 'package:sharedinbox/core/models/undo_action.dart';
@@ -517,13 +518,7 @@ class _EmailDetailScreenState extends ConsumerState<EmailDetailScreen> {
     String raw,
   ) async {
     try {
-      Directory dir;
-      try {
-        dir =
-            (await getDownloadsDirectory()) ?? (await getTemporaryDirectory());
-      } catch (_) {
-        dir = await getTemporaryDirectory();
-      }
+      final dir = await getTemporaryDirectory();
       final subject = (header?.subject ?? 'email')
           .replaceAll(RegExp(r'[^\w\s-]'), '_')
           .trim();
@@ -532,7 +527,15 @@ class _EmailDetailScreenState extends ConsumerState<EmailDetailScreen> {
       await file.writeAsString(raw);
       if (!context.mounted) return;
       ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(content: Text('Saved $filename to ${dir.path}')),
+        SnackBar(
+          content: Text('Saved $filename'),
+          action: SnackBarAction(
+            label: 'Share',
+            onPressed: () => SharePlus.instance.share(
+              ShareParams(files: [XFile(file.path)]),
+            ),
+          ),
+        ),
       );
     } catch (e) {
       if (!context.mounted) return;

pubspec.yaml

@@ -60,6 +60,7 @@ dependencies:
 
   # App version metadata for crash reports
   package_info_plus: ^8.0.0
+  share_plus: ^12.0.2
 
 dev_dependencies:
   flutter_test:

test/widget/email_detail_screen_test.dart

@@ -12,14 +12,11 @@ import 'package:sharedinbox/di.dart';
 
 import 'helpers.dart';
 
-// Fake PathProviderPlatform so _downloadRaw resolves getDownloadsDirectory /
-// getTemporaryDirectory via pure microtasks instead of calling xdg-user-dir.
+// Fake PathProviderPlatform so _downloadRaw resolves getTemporaryDirectory
+// via pure microtasks instead of calling xdg-user-dir.
 class _FakePathProviderPlatform extends PathProviderPlatform {
   @override
   Future<String?> getTemporaryPath() async => '/tmp';
-
-  @override
-  Future<String?> getDownloadsPath() async => '/tmp';
 }
 
 // IOOverrides subclass that stubs File creation so _downloadRaw completes
@@ -261,7 +258,7 @@ void main() {
       });
 
       await tester.tap(find.text('Download'));
-      // Each pump drains one microtask level: getDownloadsDirectory, then
+      // Each pump drains one microtask level: getTemporaryDirectory, then
       // writeAsString, then _downloadRaw return, then Navigator.pop.
       for (var i = 0; i < 10; i++) {
         await tester.pump(Duration.zero);
@@ -270,6 +267,8 @@ void main() {
 
       // Dialog must be dismissed after download completes.
       expect(find.text('Raw Email'), findsNothing);
+      // SnackBar with Share action must be visible.
+      expect(find.text('Share'), findsOneWidget);
     });
 
     testWidgets('Show Mail Structure opens dialog with MIME parts', (