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/external-agent-migration/src/lib.rs

@@ -1,6 +1,7 @@
 //! Migration helpers for importing external-agent configuration into Codex.
 
 mod hooks_cla;
+mod hooks_cur;
 pub mod sessions;
 
 use serde_json::Value as JsonValue;
@@ -16,6 +17,8 @@ use toml::Value as TomlValue;
 pub use hooks_cla::hook_migration_event_names_cla;
 pub use hooks_cla::hooks_migration_description_cla;
 pub use hooks_cla::import_hooks_cla;
+pub use hooks_cur::hook_migration_event_names_cur;
+pub use hooks_cur::import_hooks_cur;
 
 const SOURCE_EXTERNAL_AGENT_NAME: &str = "claude";
 const EXTERNAL_AGENT_MCP_CONFIG_FILE: &str = ".mcp.json";