fix(cli): support ctrl-arrow word navigation

[c8dhjp4tyv-bit]

Recreated on the rewritten main after #1108 was auto-closed during repository maintenance. This carries the same reviewed change set on the new history.

Summary

• support Ctrl+Left and Ctrl+Right word navigation in the CLI input
• keep existing Alt+Left/Right and Alt+B/F behavior on the same boundary helpers
• preserve Ctrl+B and Ctrl+F as single-character Emacs movement
• add focused regression coverage for Windows-style arrow navigation

Fixes #847

Validation

Prior validation before the history rewrite:

• targeted multiline-input and word-navigation tests: 77 passed
• related CLI keyboard/chat-input tests: 74 passed
• CLI typecheck: only existing missing tar and react-dom/server declarations remain
• git diff --check passes
• Prettier reports the pre-existing formatting drift in multiline-input.tsx; the base file has the same result