feat: show URL tooltip on long-press of unsubscribe chip (#294)

Wrap the ActionChip in a Tooltip whose message is the resolved
unsubscribe URI, so a long-press (mobile) or hover (desktop) reveals
the URL before the user taps.

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

lib/ui/screens/email_detail_screen.dart

@@ -938,10 +938,13 @@ class _UnsubscribeChip extends StatelessWidget {
   Widget build(BuildContext context) {
     final uri = _parseUnsubscribeUri(header);
     if (uri == null) return const SizedBox.shrink();
-    return ActionChip(
-      avatar: const Icon(Icons.unsubscribe_outlined, size: 16),
-      label: const Text('Unsubscribe'),
-      onPressed: () => launchUrl(uri, mode: LaunchMode.externalApplication),
+    return Tooltip(
+      message: uri.toString(),
+      child: ActionChip(
+        avatar: const Icon(Icons.unsubscribe_outlined, size: 16),
+        label: const Text('Unsubscribe'),
+        onPressed: () => launchUrl(uri, mode: LaunchMode.externalApplication),
+      ),
     );
   }
 }

test/widget/email_detail_screen_test.dart

@@ -475,6 +475,44 @@ void main() {
       expect(find.text('Share'), findsOneWidget);
     });
 
+    testWidgets(
+      'long-press on unsubscribe chip shows URL tooltip',
+      (tester) async {
+        final email = testEmail(
+          listUnsubscribeHeader: '<https://example.com/unsubscribe>',
+        );
+        await tester.pumpWidget(
+          buildApp(
+            initialLocation:
+                '/accounts/acc-1/mailboxes/INBOX/emails/acc-1%3A42',
+            overrides: _overrides(
+              body: const EmailBody(emailId: 'acc-1:42', attachments: []),
+              email: email,
+            ),
+          ),
+        );
+        await tester.pumpAndSettle();
+
+        expect(find.text('Unsubscribe'), findsOneWidget);
+
+        expect(
+          find.byWidgetPredicate(
+            (w) =>
+                w is Tooltip && w.message == 'https://example.com/unsubscribe',
+          ),
+          findsOneWidget,
+        );
+
+        await tester.longPress(find.text('Unsubscribe'));
+        await tester.pumpAndSettle();
+
+        expect(
+          find.text('https://example.com/unsubscribe'),
+          findsOneWidget,
+        );
+      },
+    );
+
     testWidgets('Show Mail Structure opens dialog with MIME parts', (
       tester,
     ) async {

test/widget/helpers.dart

@@ -588,6 +588,7 @@ Email testEmail({
   bool isSeen = false,
   bool isFlagged = false,
   bool hasAttachment = false,
+  String? listUnsubscribeHeader,
 }) =>
     Email(
       id: id,
@@ -603,6 +604,7 @@ Email testEmail({
       isSeen: isSeen,
       isFlagged: isFlagged,
       hasAttachment: hasAttachment,
+      listUnsubscribeHeader: listUnsubscribeHeader,
     );
 
 class FakeSearchHistoryRepository implements SearchHistoryRepository {