title_bar: Add "panel layout" menu to the user menu (#54771)

Closes https://github.com/zed-industries/zed/issues/54545

With the release of the parallel agents feature, we changed the default
panel positions optimizing for an agentic-first layout. Even though we
introduced a settings backfill _and_ the ability to revert after
interacting with the announcement toast, this change seems to be causing
a bit of frustration still. In response, this PR adds a "Panel Layout"
menu in the user menu that allows to quickly toggle between the
"Classic" layout and the "Agentic" layout. If you have a different set
up, you'll see a "custom" item there just confirming that.

| Panel Layout | Custom set up |
|--------|--------|
| <img width="1110" height="866" alt="Screenshot 2026-04-24 at 12 
52@2x"
src="https://github.com/user-attachments/assets/197fc4ec-b4b3-4b13-bcb3-9d3495cf0d0a"
/> | <img width="1156" height="866" alt="Screenshot 2026-04-24 at 12 
55@2x"
src="https://github.com/user-attachments/assets/ca791b1b-eb6a-47a9-8aa5-c2015f33e5bd"
/> |

Release Notes:

- Added a menu item in the user menu called "Panel Layout" which offers
the ability to quickly swap between the two standard panel layouts:
classic (project panel, git panel, etc., on the left) and agentic (agent
panel on the left, everything else on the right).

Cargo.lock

@@ -18159,6 +18159,7 @@ checksum = "1f3ccbac311fea05f86f61904b462b55fb3df8837a366dfc601a0161d0532f20"
 name = "title_bar"
 version = "0.1.0"
 dependencies = [
+ "agent_settings",
  "anyhow",
  "arrayvec",
  "auto_update",
@@ -18168,6 +18169,7 @@ dependencies = [
  "client",
  "cloud_api_types",
  "db",
+ "fs",
  "git_ui",
  "gpui",
  "icons",

crates/title_bar/Cargo.toml

@@ -29,8 +29,10 @@ test-support = [
 ]
 
 [dependencies]
+agent_settings.workspace = true
 anyhow.workspace = true
 auto_update.workspace = true
+fs.workspace = true
 platform_title_bar.workspace = true
 call.workspace = true
 channel.workspace = true

crates/title_bar/src/title_bar.rs

@@ -7,6 +7,7 @@ mod update_version;
 
 use crate::application_menu::{ApplicationMenu, show_menus};
 use crate::plan_chip::PlanChip;
+use agent_settings::{AgentSettings, WindowLayout};
 use arrayvec::ArrayVec;
 use git_ui::worktree_picker::WorktreePicker;
 pub use platform_title_bar::{
@@ -44,8 +45,8 @@ use std::time::Duration;
 use theme::ActiveTheme;
 use title_bar_settings::TitleBarSettings;
 use ui::{
-    Avatar, ButtonLike, ContextMenu, IconWithIndicator, Indicator, PopoverMenu, PopoverMenuHandle,
-    TintColor, Tooltip, prelude::*, utils::platform_title_bar_height,
+    Avatar, ButtonLike, ContextMenu, ContextMenuEntry, IconWithIndicator, Indicator, PopoverMenu,
+    PopoverMenuHandle, TintColor, Tooltip, prelude::*, utils::platform_title_bar_height,
 };
 use update_version::UpdateVersion;
 use util::ResultExt;
@@ -1202,6 +1203,13 @@ impl TitleBar {
                 let organizations = organizations.clone();
                 let user_store = user_store.clone();
 
+                let ai_enabled = !project::DisableAiSettings::get_global(cx).disable_ai;
+                let current_layout = AgentSettings::get_layout(cx);
+                let is_editor = matches!(current_layout, WindowLayout::Editor(_));
+                let is_agent = matches!(current_layout, WindowLayout::Agent(_));
+                let is_custom = matches!(current_layout, WindowLayout::Custom(_));
+                let fs = <dyn fs::Fs>::global(cx);
+
                 ContextMenu::build(window, cx, |menu, _, _cx| {
                     menu.when(is_signed_in, |this| {
                         let user_login = user_login.clone();
@@ -1311,6 +1319,46 @@ impl TitleBar {
                         "Extensions",
                         zed_actions::Extensions::default().boxed_clone(),
                     )
+                    .when(ai_enabled, |menu| {
+                        let fs = fs.clone();
+                        menu.separator()
+                            .submenu("Panel Layout", move |menu, _window, _cx| {
+                                let fs = fs.clone();
+                                menu.toggleable_entry(
+                                    "Classic",
+                                    is_editor,
+                                    IconPosition::Start,
+                                    None,
+                                    {
+                                        let fs = fs.clone();
+                                        move |_window, cx| {
+                                            drop(AgentSettings::set_layout(
+                                                WindowLayout::Editor(None),
+                                                fs.clone(),
+                                                cx,
+                                            ));
+                                        }
+                                    },
+                                )
+                                .toggleable_entry("Agentic", is_agent, IconPosition::Start, None, {
+                                    let fs = fs.clone();
+                                    move |_window, cx| {
+                                        drop(AgentSettings::set_layout(
+                                            WindowLayout::Agent(None),
+                                            fs.clone(),
+                                            cx,
+                                        ));
+                                    }
+                                })
+                                .when(is_custom, |menu| {
+                                    menu.item(
+                                        ContextMenuEntry::new("Custom")
+                                            .toggleable(IconPosition::Start, true)
+                                            .disabled(true),
+                                    )
+                                })
+                            })
+                    })
                     .when(is_signed_in, |this| {
                         this.separator()
                             .action("Sign Out", client::SignOut.boxed_clone())