feat: adopt smolmail protocol 1.1, adaptive nav shell, and server mail retention

lib/presentation/screens/inbox_screen.dart

@@ -4,18 +4,46 @@ import "package:flutter_riverpod/flutter_riverpod.dart";
 
 import "package:smol_mail/data/providers/providers.dart";
 import "package:smol_mail/presentation/routes/app_router.gr.dart";
-import "package:smol_mail/presentation/widgets/drawer/app_drawer.dart";
 import "package:smol_mail/presentation/widgets/image_banner.dart";
 import "package:smol_mail/presentation/widgets/message/message_list.dart";
 import "package:smol_mail/shared/utils/snackbar.dart";
 import "package:smol_mail/smol/errors.dart";
 
+const _folders = ["inbox", "requests", "sent"];
+
 /// No server push in v1 (SPEC.md §13): new mail arrives when the user taps
-/// fetch, which pulls everything and acknowledges what verifies.
+/// fetch, which pulls everything and acknowledges what verifies. One FETCH
+/// call populates both Inbox and Requests (they're tiers of the same
+/// mailbox), so both — but not the purely local Sent folder — offer fetch.
 @RoutePage()
-class InboxScreen extends ConsumerWidget {
+class InboxScreen extends ConsumerStatefulWidget {
   const InboxScreen({super.key});
 
+  @override
+  ConsumerState<InboxScreen> createState() => _InboxScreenState();
+}
+
+class _InboxScreenState extends ConsumerState<InboxScreen>
+    with SingleTickerProviderStateMixin {
+  late final TabController _tabController;
+
+  @override
+  void initState() {
+    super.initState();
+    _tabController = TabController(length: _folders.length, vsync: this)
+      ..addListener(() {
+        // Fires once settled, whether the change came from a tap or a swipe;
+        // only the AppBar's fetch button depends on which tab is active.
+        if (!_tabController.indexIsChanging) setState(() {});
+      });
+  }
+
+  @override
+  void dispose() {
+    _tabController.dispose();
+    super.dispose();
+  }
+
   Future<void> _fetch(BuildContext context, WidgetRef ref) async {
     final client = ref.read(clientProvider);
     try {
@@ -36,47 +64,63 @@ class InboxScreen extends ConsumerWidget {
     }
   }
 
+  Widget _folderView(BuildContext context, WidgetRef ref, String folder) {
+    final messages = ref.watch(messagesForFolderProvider(folder));
+    final canFetch = folder != "sent";
+    final onRefresh = canFetch ? () => _fetch(context, ref) : () => Future.value();
+
+    if (messages.isEmpty) {
+      return RefreshIndicator(
+        onRefresh: onRefresh,
+        child: ListView(
+          children: const [
+            ImageBanner(
+              imgSrc: "assets/images/empty.png",
+              text: "Nothing here yet!",
+            ),
+          ],
+        ),
+      );
+    }
+    return MessageList(folder: folder, onRefresh: onRefresh);
+  }
+
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
-    final messages = ref.watch(messagesProvider);
-    final folder = ref.watch(folderProvider);
+  Widget build(BuildContext context) {
+    final unread = ref.watch(unreadProvider);
+    final requestsUnread = ref.watch(requestsUnreadProvider);
+    final canFetch = _folders[_tabController.index] != "sent";
 
     return Scaffold(
       appBar: AppBar(
-        title: Text(folder == "inbox" ? "Inbox" : "Sent"),
+        title: const Text("kirakira"),
         actions: [
-          if (folder == "inbox")
+          if (canFetch)
             IconButton(
               tooltip: "Fetch",
               onPressed: () => _fetch(context, ref),
               icon: const Icon(Icons.cloud_download),
             ),
         ],
+        bottom: TabBar(
+          controller: _tabController,
+          tabs: [
+            Tab(text: unread > 0 ? "Inbox ($unread)" : "Inbox"),
+            Tab(text: requestsUnread > 0 ? "Requests ($requestsUnread)" : "Requests"),
+            const Tab(text: "Sent"),
+          ],
+        ),
       ),
-      drawer: const AppDrawer(),
       floatingActionButton: FloatingActionButton(
         onPressed: () => AutoRouter.of(context).push(ComposeRoute()),
         child: const Icon(Icons.edit),
       ),
-      body: messages.isEmpty
-          ? RefreshIndicator(
-              onRefresh: () => folder == "inbox"
-                  ? _fetch(context, ref)
-                  : Future.value(),
-              child: ListView(
-                children: const [
-                  ImageBanner(
-                    imgSrc: "assets/images/empty.png",
-                    text: "Nothing here yet!",
-                  ),
-                ],
-              ),
-            )
-          : MessageList(
-              onRefresh: () => folder == "inbox"
-                  ? _fetch(context, ref)
-                  : Future.value(),
-            ),
+      body: TabBarView(
+        controller: _tabController,
+        children: [
+          for (final folder in _folders) _folderView(context, ref, folder),
+        ],
+      ),
     );
   }
 }