feat(settings): Session tabs toggle in General → Navigation

A new Session tabs group (web/desktop only) turns the header session
tabs off; disabled, the header renders the exact pre-tabs view — plain
session title with meta row and the always-visible session menu (the
same block VS Code uses). The Alt+W close-tab shortcut no-ops while
tabs are off. Registered in settings search with a matching anchor;
labels translated in all locales.

packages/ui/src/stores/useUIStore.ts

@@ -750,6 +750,8 @@ interface UIStore {
   maxLastMessageLength: number; // chars — truncate {last_message} when summarization is off
 
   showTerminalQuickKeysOnDesktop: boolean;
+  /** Header session tabs (web/desktop). Off restores the plain session title. */
+  sessionTabsEnabled: boolean;
   persistChatDraft: boolean;
   showOpenCodeUpdateNotifications: boolean;
   agentControlToolEnabled: boolean;
@@ -920,6 +922,7 @@ interface UIStore {
   setNativeNotificationsEnabled: (value: boolean) => void;
   setNotificationMode: (mode: 'always' | 'hidden-only') => void;
   setShowTerminalQuickKeysOnDesktop: (value: boolean) => void;
+  setSessionTabsEnabled: (value: boolean) => void;
   setNotifyOnSubtasks: (value: boolean) => void;
   setDockBadgeEnabled: (value: boolean) => void;
   setNotifyOnCompletion: (value: boolean) => void;
@@ -1092,6 +1095,7 @@ export const useUIStore = create<UIStore>()(
         maxLastMessageLength: 250,
 
         showTerminalQuickKeysOnDesktop: false,
+        sessionTabsEnabled: true,
         persistChatDraft: true,
         showOpenCodeUpdateNotifications: !isWindowsArm64(),
         agentControlToolEnabled: true,
@@ -2244,6 +2248,10 @@ export const useUIStore = create<UIStore>()(
           set({ showTerminalQuickKeysOnDesktop: value });
         },
 
+        setSessionTabsEnabled: (value) => {
+          set({ sessionTabsEnabled: value });
+        },
+
         setNotifyOnSubtasks: (value) => {
           set({ notifyOnSubtasks: value });
         },
@@ -2672,6 +2680,7 @@ export const useUIStore = create<UIStore>()(
           nativeNotificationsEnabled: state.nativeNotificationsEnabled,
           notificationMode: state.notificationMode,
           showTerminalQuickKeysOnDesktop: state.showTerminalQuickKeysOnDesktop,
+          sessionTabsEnabled: state.sessionTabsEnabled,
           notifyOnSubtasks: state.notifyOnSubtasks,
           dockBadgeEnabled: state.dockBadgeEnabled,
           notifyOnCompletion: state.notifyOnCompletion,