Ctrl+C stash drops large paste payloads when recalling history in TUI

Summary

When a large paste is collapsed into a placeholder (e.g., "[Pasted Content ... chars]"), pressing Ctrl+C stashes the draft, but recalling it with Up-arrow loses the hidden payload. The placeholder remains as plain white text and submits literally, which effectively discards the original paste.

Steps to Reproduce

1. Run Codex (either with TUI or --enable tui2)
2. Paste a large chunk of text so it collapses into a "[Pasted Content ... chars]" placeholder.
3. Press Ctrl+C to stash the draft.
4. Press Up-arrow to recall the draft from history.
5. Submit the message or inspect the placeholder styling.

Expected

• The recalled draft preserves the hidden pasted content.
• The placeholder stays styled (blue) and expands to the original content on submit.

Actual

• The placeholder becomes plain text (white) with no hidden payload.
• Submitting sends the literal placeholder text, losing the original paste.