Add Word-wise Deletion in TUI

Summary
In Codex CLI on macOS, pressing Option+Delete (⌥⌫) currently deletes only a single character. This diverges from expected macOS behavior, where ⌥⌫ deletes the previous word and accelerates when held.

Current Behavior

• ⌥⌫ deletes one character at a time.
• No support for word-wise deletion or fast repeat while held.

Expected Behavior

• ⌥⌫ deletes the previous word.
• Holding the keys rapidly deletes multiple words (sentence-level speed), consistent with native macOS editors and tools like Claude Code.

Motivation
Word-wise deletion is a standard editing shortcut on macOS. Adding it to Codex CLI improves text editing efficiency and aligns with user expectations.

Steps to Reproduce

1. On macOS (Terminal.app or iTerm2), launch Codex CLI.
2. Type a sentence in the input field.
3. Press Option+Delete (⌥⌫).
4. Observe that only a single character is deleted.

Environment

• macOS Sonoma/Sequoia (14/15)
• Codex CLI (TUI): latest

Are you interested in implementing this feature?

_No response_

Additional information

_No response_