tui: add codex resume --history-lines to cap replayed scrollback

Summary

Add a codex resume --history-lines <LINES> option to cap replayed scrollback output when resuming a session.

Why

For long sessions, codex resume can spend noticeable time printing a large backlog before the prompt is usable. In practice, most of that output is low-value when the goal is to quickly continue work.

A replay line cap makes resume startup faster and keeps terminal output focused on recent context.

Proposed behavior

• New flag: codex resume --history-lines <positive-int>
• Applies only to replayed resume output (not normal live output after startup)
• Default behavior remains unchanged when the flag is omitted

Ready implementation

I have a complete, tested implementation in my fork:

• Branch: https://github.com/wegel/codex/tree/pr/history-lines-limit
• Compare: https://github.com/openai/codex/compare/main...wegel:pr/history-lines-limit?expand=1
• Commit: b6480fa365fdf10dadb0c6532f92ff1cb1952383

Validation run

• cargo test -p codex-cli resume_history_lines_flag_sets_limit -- --nocapture