fix(cli): standard text-editing keys in AI question prompt

[cmp0xff]

Summary

Fix text-editing keys in the AI question prompt ("Other" free-text answer).

Changes

• Cursor-aware editing in the "Other" answer box: ←/→, Alt/Ctrl+←/→ word movement, Home/End, Ctrl+A/E/B/F/W/U/K, Alt+B/F/D, Backspace/Delete.
• Fixes arrow keys inserting [D/[C/[H/[F garbage in that box.
• Parser now recognizes application-cursor-mode arrows (ESCOD/ESCOC) and Ctrl+Home/End.
• READMEs document per-platform key mappings (Linux / macOS / Windows).

Verification

• 318 tests pass; typecheck, lint, and prettier clean.
• Keybindings aligned with the standard terminal editing keys used by Claude Code CLI and OpenAI Codex CLI.

[cmp0xff]

@qorzj 您好，我是 deepcode-cli 用户，希望为客户端作一点贡献，请拨冗斧正，感谢！如果倾向于用户提交 issue 而非 PR，也烦请告知。

[qorzj]

@cmp0xff 感谢，这个PR解决了一个长期存在的问题。自动测试和人工测试都已通过，已合并。