TUI: Add session resume picker (--resume) and quick resume (--continue) (#3135)

Adds a TUI resume flow with an interactive picker and quick resume.

- CLI: 
  - --resume / -r: open picker to resume a prior session
  - --continue   / -l: resume the most recent session (no picker)
- Behavior on resume: initial history is replayed, welcome banner
hidden, and the first redraw is suppressed to avoid flicker.
- Implementation:
- New tui/src/resume_picker.rs (paginated listing via
RolloutRecorder::list_conversations)
  - App::run accepts ResumeSelection; resumes from disk when requested
- ChatWidget refactor with ChatWidgetInit and new_from_existing; replays
initial messages
- Tests: cover picker sorting/preview extraction and resumed-history
rendering.
- Docs: getting-started updated with flags and picker usage.



https://github.com/user-attachments/assets/1bb6469b-e5d1-42f6-bec6-b1ae6debda3b

codex-rs/core/src/lib.rs

@@ -61,7 +61,10 @@ pub mod spawn;
 pub mod terminal;
 mod tool_apply_patch;
 pub mod turn_diff_tracker;
+pub use rollout::RolloutRecorder;
+pub use rollout::list::ConversationItem;
 pub use rollout::list::ConversationsPage;
+pub use rollout::list::Cursor;
 mod user_notification;
 pub mod util;
 pub use apply_patch::CODEX_APPLY_PATCH_ARG1;