Alt-d should delete the next word. It didn’t. Now it does. Added a small
test so it stays that way.
Details:
File updated:
[codex-rs/tui/src/bottom_pane/textarea.rs](./codex-rs/tui/src/bottom_pane/textarea.rs)
Test added: delete_forward_word_alt_d — verifies Alt-d deletes the next
word and keeps the cursor position correct.
Solves Issue #12453
