windows-sandbox: feed setup from resolved permissions (#23167)

## Why

This is the next step in the Windows sandbox migration away from the
legacy `SandboxPolicy` abstraction. #22923 moved write-root and token
decisions onto `ResolvedWindowsSandboxPermissions`, but setup and
identity still accepted `SandboxPolicy` and converted internally. This
PR pushes that conversion outward so the setup path consumes the
resolved Windows permission view directly.

## What Changed

- Changed `SandboxSetupRequest` to carry
`ResolvedWindowsSandboxPermissions` instead of `SandboxPolicy` plus
policy cwd.
- Updated setup refresh/elevation and identity credential preparation to
use resolved permissions for read roots, write roots, network identity,
and deny-write payload planning.
- Removed the production `allow.rs` legacy wrapper; allow-path
computation now takes resolved permissions directly.
- Added a permissions-based world-writable audit entry point while
keeping the existing legacy wrapper for compatibility.
- Updated legacy ACL setup and the core Windows setup bridge to
construct resolved permissions at the boundary.
- Hardened the Windows sandbox integration test helper staging so Bazel
retries can reuse an already-staged helper if a prior sandbox helper
process still has the executable open.

## Verification

- `cargo test -p codex-windows-sandbox`
- `cargo test -p codex-core --test all --no-run`
- `just fix -p codex-windows-sandbox`
- `just fix -p codex-core`
- Attempted `cargo check -p codex-windows-sandbox --target
x86_64-pc-windows-gnullvm`, but the local machine is missing
`x86_64-w64-mingw32-clang`; Windows CI should cover that target.











---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/23167).
* #23715
* #23714
* __->__ #23167

codex-rs/core/tests/suite/windows_sandbox.rs

@@ -93,7 +93,22 @@ fn stage_windows_sandbox_helpers() -> anyhow::Result<()> {
     for helper_name in ["codex-windows-sandbox-setup", "codex-command-runner"] {
         let helper = codex_utils_cargo_bin::cargo_bin(helper_name)?;
         let file_name = Path::new(helper_name).with_extension("exe");
-        std::fs::copy(helper, resources_dir.join(file_name))?;
+        let destination = resources_dir.join(file_name);
+        if let Err(err) = std::fs::copy(&helper, &destination) {
+            // A sandbox helper can briefly remain alive after the sandboxed
+            // command exits. Bazel may retry the test while that process still
+            // has the staged executable open, so keep the already-staged copy.
+            if err.kind() == std::io::ErrorKind::PermissionDenied && destination.exists() {
+                continue;
+            }
+            return Err(err).with_context(|| {
+                format!(
+                    "stage Windows sandbox helper {} at {}",
+                    helper.display(),
+                    destination.display()
+                )
+            });
+        }
     }
     Ok(())
 }