## 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>
iceweasel-oaiandGitHub
