## What changed
- Report `windows_mxc` from native MXC availability on Windows.
- Allow MXC TTY launches and managed networking, using dedicated proxy listeners without requiring a shared-ingress restricting SID.
- Reject MXC custom `argv0` and private-desktop launches, and continue failing closed when native MXC is unavailable.
## Testing
Extend the Windows remote sandbox process-write test to cover MXC with both pipes and ConPTY. Retain coverage for rejecting MXC requests when native support is unavailable.
GitOrigin-RevId: 80c5f319b9066d06b26f0a7eb7119a109e6ebef7