Add Cursor support to setup import (#33426)

## What changed

- Detect and import supported Cursor settings, sandbox permissions, MCP servers,
  project instructions, hooks, agents, commands, plugins, and recent chat
  sessions.
- Update the `/import` flow to check Claude Code and Cursor, prompting for a
  source when both have importable data.
- Add `migrationSource` to the app-server detect and import requests so each
  operation uses the selected adapter, while retaining `source` for import
  attribution and backwards compatibility.

## Testing

- Add coverage for Cursor config conversion, hooks, plugins, session discovery
  and conversion, app-server imports, and TUI source selection.

GitOrigin-RevId: a65a1511b6c1c2f9e3e0cfe4f816bb435807282e

codex-rs/tui/src/external_agent_config_migration_source_tests.rs

@@ -0,0 +1,42 @@
+use super::*;
+use crate::test_backend::VT100Backend;
+use crossterm::event::KeyEvent;
+use crossterm::event::KeyModifiers;
+use pretty_assertions::assert_eq;
+use ratatui::Terminal;
+
+fn new_screen() -> ExternalAgentConfigSourceScreen {
+    ExternalAgentConfigSourceScreen::new(
+        FrameRequester::test_dummy(),
+        &ExternalAgentConfigMigrationSource::ALL,
+    )
+}
+
+#[test]
+fn external_agent_config_source_prompt_snapshot() {
+    let screen = new_screen();
+    let mut terminal =
+        Terminal::new(VT100Backend::new(/*width*/ 80, /*height*/ 12)).expect("terminal");
+    terminal
+        .draw(|frame| frame.render_widget_ref(&screen, frame.area()))
+        .expect("render source prompt");
+    insta::assert_snapshot!("external_agent_config_source_prompt", terminal.backend());
+}
+
+#[test]
+fn external_agent_config_source_prompt_selects_highlighted_source() {
+    let mut screen = new_screen();
+    screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
+    screen.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
+    assert_eq!(
+        screen.selection(),
+        Some(ExternalAgentConfigMigrationSource::Cur)
+    );
+}
+
+#[test]
+fn external_agent_config_source_prompt_can_cancel() {
+    let mut screen = new_screen();
+    screen.handle_key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
+    assert_eq!(screen.selection(), None);
+}