Clarify Git worktree choices for new and forked conversations (#50416)

## What changed

Label the `/new` and `/fork` picker options “Use current Git worktree” and “Create new Git worktree”. Explain that creating a worktree makes a separate checkout of the repository in another directory.

## Testing

Update picker assertions and snapshots for both commands to cover the revised labels and description.

GitOrigin-RevId: b7fb1aac3107e39c324707f9ae69c210a97346d7

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__worktrees_fork_choices.snap

@@ -5,7 +5,8 @@ expression: popup
   Where should the forked conversation run?
 
 
-› 1. Current checkout  Keep using the current working directory
-  2. New worktree      Create an isolated managed checkout
+› 1. Use current Git worktree  Keep using the current working directory
+  2. Create new Git worktree   Create a separate checkout of this repository in
+                               another directory
 
   enter select · esc back

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__worktrees_new_choices.snap

@@ -5,7 +5,8 @@ expression: popup
   Where should the new conversation run?
 
 
-› 1. Current checkout  Keep using the current working directory
-  2. New worktree      Create an isolated managed checkout
+› 1. Use current Git worktree  Keep using the current working directory
+  2. Create new Git worktree   Create a separate checkout of this repository in
+                               another directory
 
   enter select · esc back

codex-rs/tui/src/chatwidget/tests/worktree_picker_tests.rs

@@ -32,8 +32,8 @@ async fn slash_new_and_fork_offer_checkout_choices_inside_local_git_repository()
     chat.dispatch_command(SlashCommand::New);
     let popup = render_bottom_popup(&chat, /*width*/ 80);
     assert_chatwidget_snapshot!("worktrees_new_choices", popup);
-    assert!(popup.contains("Current checkout"), "popup: {popup}");
-    assert!(popup.contains("New worktree"), "popup: {popup}");
+    assert!(popup.contains("Use current Git worktree"), "popup: {popup}");
+    assert!(popup.contains("Create new Git worktree"), "popup: {popup}");
     assert_matches!(rx.try_recv(), Err(TryRecvError::Empty));
     chat.handle_key_event(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
     chat.bottom_pane

codex-rs/tui/src/chatwidget/worktree_picker.rs

@@ -46,7 +46,7 @@ impl ChatWidget {
             title: Some(title.into()),
             items: vec![
                 SelectionItem {
-                    name: "Current checkout".to_string(),
+                    name: "Use current Git worktree".to_string(),
                     description: Some("Keep using the current working directory".to_string()),
                     actions: vec![Box::new(move |tx| match mode {
                         ManagedWorktreeMode::New => {
@@ -64,8 +64,11 @@ impl ChatWidget {
                     ..Default::default()
                 },
                 SelectionItem {
-                    name: "New worktree".to_string(),
-                    description: Some("Create an isolated managed checkout".to_string()),
+                    name: "Create new Git worktree".to_string(),
+                    description: Some(
+                        "Create a separate checkout of this repository in another directory"
+                            .to_string(),
+                    ),
                     actions: vec![Box::new(move |tx| {
                         tx.send(AppEvent::StartManagedWorktree {
                             mode,