This pr addresses the fix for
https://github.com/openai/codex/issues/2713
### Changes:
- Added key handler for `Alt+Ctrl+H` → `delete_backward_word()`
- Added test coverage in `delete_backward_word_alt_keys()` that verifies
both:
- Standard `Alt+Backspace` binding continues to work
- New `Alt+Ctrl+H` binding works correctly for backward word deletion
### Testing:
The test ensures both key combinations produce identical behavior:
- Delete the previous word from "hello world" → "hello "
- Cursor positioned correctly after deletion
### Backward Compatibility:
This change is backward compatible - existing `Alt+Backspace`
functionality remains unchanged while adding support for the
terminal-specific `Alt+Ctrl+H` variant
fb3f6456cf