[BUG] Ctrl+W, Shift+Tab, Alt+V stopped working in Claude Code on Windows (regression)

Description

Several readline/terminal keybindings stopped working inside Claude Code's TUI on Windows. They worked until approximately one week ago (around v2.1.7x).

Key finding: Ctrl+W works in Git Bash inside VS Code's integrated terminal before launching Claude Code, but stops working after Claude Code starts. This confirms the issue is in Claude Code's TUI input handler, not VS Code or the terminal emulator.

Affected Keys

| Key | Expected behavior | Actual behavior |
|---|---|---|
| Ctrl+W | Delete previous word (readline) | Nothing happens — keystroke is swallowed |
| Shift+Tab | Pass through to shell | Captured by chat:cycleMode (new default?) |
| Alt+V | Pass through to shell | Captured by chat:imagePaste |
| Ctrl+C | Interrupt / expected terminal behavior | Inconsistent behavior |

Steps to Reproduce

1. Open VS Code with Git Bash as integrated terminal
2. In the terminal, type some text and press Ctrl+W — it deletes the previous word ✓
3. Run claude in the same terminal
4. Type some text in the Claude Code chat input
5. Press Ctrl+W — nothing happens ✗

Expected Behavior

Ctrl+W should delete the previous word in the chat input, as it does in any readline-based terminal input. Keys not bound to Claude Code actions should pass through to standard text editing.

Context

• This is a regression — these keys worked ~1 week ago
• Related to #22626 (unbinding keys via null swallows keystrokes instead of passing through)
• Related to #29931 (Ctrl+B passthrough blocked)
• Related to #38354 (Ctrl+W word boundary issues — different bug, that one is about Bun's Intl.Segmenter)

Environment

• Claude Code: 2.1.83
• Claude Code VS Code extension: 2.1.83
• VS Code: 1.113.0
• OS: Windows 10 Pro 10.0.19045 (running in Parallels VM on macOS)
• Shell: Git Bash
• Terminal: VS Code integrated terminal