Add working-directory commands to the TUI (#38894)

## What changed

- Add `/cd [path]` for changing an idle local session's working directory while preserving conversation history. Relative paths resolve from the current directory, and omitting the path selects `~`.
- Reload project configuration, instructions, permissions, keybindings, file search, and hooks for the destination before replacing the active session.
- Reject unsafe transitions, including active or queued work, background terminals, remote environments, untrusted destinations, and incompatible permission profiles.
- Add `/pwd` and its `/cwd` alias to display the current working directory, and discard asynchronous results left over from the previous directory.

## Testing

- Cover command parsing, aliases, default paths, session eligibility, transition failures, history preservation, destination policy loading, hooks, and stale events.

GitOrigin-RevId: 1a987c029f157a087ba02c0f26e022260409132b

codex-rs/tui/src/chatwidget.rs

@@ -438,6 +438,7 @@ mod turn_runtime;
 use self::turn_lifecycle::TurnLifecycleState;
 mod usage;
 mod user_messages;
+mod working_directory;
 use self::user_messages::PendingSteer;
 use self::user_messages::PendingSteerCompareKey;
 use self::user_messages::QueueDrain;