Windows Terminal Preview duplicates non-ASCII input in Codex TUI under WSL

Environment

• Codex CLI: 0.146.0
• Platform: WSL 2 on Windows
• Terminal: Windows Terminal Preview 1.25.1912.0
• Shell: zsh
• Keyboard layout: Czech

Reproduction

1. Open Windows Terminal Preview and start a WSL shell.
2. Run codex and focus the chat composer.
3. Type a non-ASCII Czech-layout character, for example ě, š, č, ř, ž, ý, á, í, é, ú, ů, §, or '.

Actual behavior

Each affected character is inserted twice. One copy appears on key-down and the second appears when the key is released. This happens only in Codex's TUI composer; the same keyboard and terminal work correctly in the WSL shell and other TUI CLI applications.

Expected behavior

Each keypress should insert exactly one character.

Context

Windows Terminal Preview 1.25's Kitty Keyboard Protocol support fixes important input behavior in Codex, including Ctrl+Backspace word deletion and modifier-aware Enter handling. Disabling keyboard enhancement avoids this duplication, but gives up those improvements, so it is not a viable workaround.

This appears to match the already-written minimal fix in #30480, which removes REPORT_ALTERNATE_KEYS. Its PR description/comment explicitly notes that some Kitty-protocol terminals emit duplicate non-ASCII text when alternate keycodes are requested. That PR was automatically closed after 14 days without review activity, rather than rejected on technical grounds.

Relevant current code: https://github.com/openai/codex/blob/main/codex-rs/tui/src/tui/keyboard_modes.rs

Start in codex-rs/tui/src/tui/keyboard_modes.rs and compare the current Kitty Keyboard Protocol settings with the minimal change described in issue #30480. Reproduce the Czech-layout input case in Windows Terminal Preview under WSL, then verify that each listed non-ASCII key produces exactly one character while the existing modifier behavior remains intact.