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.











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[//]: # (BEGIN SAPLING FOOTER)
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with [ReviewStack](https://reviewstack.dev/openai/codex/pull/23167).
* #23715
* #23714
* __->__ #23167

codex-rs/windows-sandbox-rs/src/unified_exec/backends/legacy.rs

@@ -318,8 +318,7 @@ pub(crate) async fn spawn_windows_sandbox_session_legacy(
     allow_null_device_for_workspace_write(common.uses_write_capabilities);
 
     apply_legacy_session_acl_rules(
-        &common.policy,
-        sandbox_policy_cwd,
+        &common.permissions,
         codex_home,
         &common.current_dir,
         &env_map,