Add avatar-menu navigation style and inline Android search bar

- New Settings > Appearance > "Navigation menu" toggle
  (SettingsController.navMenuStyle, NooNavMenuStyle.drawer/avatarMenu):
  the hamburger-opens-a-Drawer pattern stays the default, or the avatar
  button opens a full-width dropdown (showAvatarMenu) instead, holding
  the same hidden-tabs + Settings content the drawer does. Removes one
  of the two top-corner targets the shell asks a thumb to reach, with
  no permanent chrome added.
- NooTopBar gains androidTitleReplacement so Android's top bar can swap
  its title for an inline search-field-styled launcher
  (ShellSearchLauncher) when search isn't in the bottom bar, instead of
  a bare search icon beside it.
- ShellAvatarButton's onTap/label are now overridable so AppTopBar can
  repoint it per the new setting without this file depending on
  avatar_menu.dart (which already depends on it for shared helpers).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/widgets/app_top_bar.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 import '../models/app_tab.dart';
+import 'avatar_menu.dart';
 import 'create_menu.dart';
 import 'noo/nav/noo_top_bar.dart';
 import 'shell/shell_common.dart';
@@ -13,8 +14,11 @@ import 'shell/shell_common.dart';
 /// - iOS: `menu` leading, `plus` (Files only - no tab besides Files has a
 ///   create/upload flow) and the account avatar trailing, then the large
 ///   title, then an inline search field that opens [SearchView].
-/// - Android: `menu`, title, `search` and avatar actions. Upload has no
-///   top-bar icon here - it's the [NooFab] `MainShellView` shows instead.
+/// - Android: `menu`, title, avatar actions. Upload has no top-bar icon
+///   here - it's the [NooFab] `MainShellView` shows instead. When search
+///   isn't in the bottom bar, the title itself is replaced by an inline
+///   search-field-styled launcher (`androidTitleReplacement`) rather than
+///   a bare search icon sitting beside it.
 ///
 /// [style] is resolved by the caller (`NooLayout.navStyle`) rather than
 /// read from context here, since [preferredSize] is a plain getter with no
@@ -22,17 +26,24 @@ import 'shell/shell_common.dart';
 /// [searchInBottomBar] is [SettingsController.searchInBottomBar], passed in
 /// for the same reason: it hides this bar's own search field/icon so
 /// there's only ever one search entry point on screen once the bottom bar
-/// has taken it over.
+/// has taken it over. [navMenuStyle] is
+/// [SettingsController.navMenuStyle]: [NooNavMenuStyle.drawer] wires the
+/// `menu` icon to `Scaffold.of(context).openDrawer()` as before;
+/// [NooNavMenuStyle.avatarMenu] drops that icon (`onMenu: null`) and makes
+/// the avatar button open `showAvatarMenu` instead of the account
+/// switcher.
 class AppTopBar extends StatelessWidget implements PreferredSizeWidget {
   final NooNavStyle style;
   final AppTab tab;
   final bool searchInBottomBar;
+  final NooNavMenuStyle navMenuStyle;
 
   const AppTopBar({
     super.key,
     required this.style,
     required this.tab,
     this.searchInBottomBar = false,
+    this.navMenuStyle = NooNavMenuStyle.drawer,
   });
 
   bool get _ios => style == NooNavStyle.ios;
@@ -53,21 +64,31 @@ class AppTopBar extends StatelessWidget implements PreferredSizeWidget {
     return NooTopBar(
       style: style,
       title: tab.label,
-      onMenu: () => Scaffold.of(context).openDrawer(),
+      onMenu: navMenuStyle == NooNavMenuStyle.drawer
+          ? () => Scaffold.of(context).openDrawer()
+          : null,
+      // Android has no large title to put a second search row under the
+      // way iOS does (`search:` below) - an inline bar replaces the title
+      // itself instead of sitting beside it as a plain icon action.
+      androidTitleReplacement: !_ios && _showSearch
+          ? const ShellSearchLauncher()
+          : null,
       actions: [
-        if (!_ios && _showSearch)
-          NooTopBarButton(
-            icon: LucideIcons.search,
-            tooltip: 'Search',
-            onTap: () => openSearch(context),
-          ),
         if (_ios && tab == AppTab.files)
           NooTopBarButton(
             icon: LucideIcons.plus,
             tooltip: 'Create',
             onTap: () => showCreateMenu(context),
           ),
-        ShellAvatarButton(hitBox: _ios ? 44 : 48),
+        ShellAvatarButton(
+          hitBox: _ios ? 44 : 48,
+          onTap: navMenuStyle == NooNavMenuStyle.avatarMenu
+              ? () => showAvatarMenu(context)
+              : null,
+          label: navMenuStyle == NooNavMenuStyle.avatarMenu
+              ? 'Menu'
+              : 'Accounts',
+        ),
       ],
       search: _ios && _showSearch ? const ShellSearchLauncher(ios: true) : null,
     );