[BUG] Title: VS Code extension crashes on CPUs without AVX support (Bun panic)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The Claude Code VS Code extension fails to launch on Windows machines with CPUs that lack AVX instruction support. The bundled Bun
runtime crashes immediately with a panic.

Environment

• OS: Windows 10 Pro 10.0.18362
• VS Code Extension Version: 2.1.86
• Bun Version (bundled): 1.3.11

What Should Happen?

The extension should either work on non-AVX CPUs or show a clear error message explaining the requirement.

Notes

• The CLI version (@anthropic-ai/claude-code via npm/Node.js) works perfectly on the same machine
• The issue is specifically with the native binary at resources\native-binary\claude.exe which bundles Bun
• A possible fix would be to fall back to the Node.js-based CLI when the native binary is unavailable or crashes

Error Messages/Logs

Bun v1.3.11 (759ce802) Windows x64 (baseline)
  Windows v.win10_19h1
  Features: no_avx2 no_avx
  CPU lacks AVX support. Please consider upgrading to a newer CPU.
  panic(thread 4608): attempt to use null value
  oh no: Bun has crashed. This indicates a bug in Bun, not your code.
  https://bun.report/1.3.11/e_1759ce80AggggggDmps5G43zv4DCAoi+FCAitqbA0

  The process exits with code 3. This happens every time the extension tries to spawn Claude, making the embedded chat panel
  completely unusable.

Steps to Reproduce

1. Install Claude Code extension (v2.1.86) in VS Code
2. Open any project
3. Open the Claude Code chat panel
4. Extension crashes immediately

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.1.86

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_