## Summary
Fix the Windows sandbox PTY spawn path to pass the pseudoconsole handle
value directly into `UpdateProcThreadAttribute`.
## Why
Sandboxed `unified_exec` PTY sessions on Windows were failing during
child process startup with `0xc0000142` (`STATUS_DLL_INIT_FAILED`). In
practice this showed up as PowerShell DLL init popups when the sandboxed
background-terminal path tried to launch an interactive shell.
The root cause was that we were passing a pointer to a local `isize`
variable instead of the pseudoconsole handle value in the form Windows
expects for `PROC_THREAD_ATTRIBUTE_PSEUDOCONSOLE`.
## Validation
- `cargo build -p codex-windows-sandbox --bins`
- Reproduced the real sandboxed `codex exec` flow with
`windows.sandbox_private_desktop=true`
- Verified a `tty=true` interactive session launched through the normal
PowerShell wrapper, printed `READY`, accepted follow-up stdin, and
exited cleanly
- Confirmed no new `0xc0000142` / `Application Popup` events appeared
after the successful repro
## Summary
This is the runtime/foundation half of the Windows sandbox unified-exec
work.
- add Windows sandbox `unified_exec` session support in
`windows-sandbox-rs` for both:
- the legacy restricted-token backend
- the elevated runner backend
- extend the PTY/process runtime so driver-backed sessions can support:
- stdin streaming
- stdout/stderr separation
- exit propagation
- PTY resize hooks
- add Windows sandbox runtime coverage in `codex-windows-sandbox` /
`codex-utils-pty`
This PR does **not** enable Windows sandbox `UnifiedExec` for product
callers yet because hooking this up to app-server comes in the next PR.
Windows sandbox advertising is intentionally kept aligned with `main`,
so sandboxed Windows callers still fall back to `ShellCommand`.
This PR isolates the runtime/session layer so it can be reviewed
independently from product-surface enablement.
---------
Co-authored-by: jif-oai <jif@openai.com>
Co-authored-by: Codex <noreply@openai.com>