Enable sandboxed V8 for code mode (#36374)

## Why

Code mode must link against a V8 build with sandbox support, but Windows MSVC
still used upstream non-sandboxed prebuilts and package builds selected the
older release artifact profile.

## What changed

- Enable the `v8_enable_sandbox` feature directly for the code mode runtime.
- Select the `ptrcomp_sandbox_release` archive and bindings in Cargo packaging
  and CI, including Windows MSVC release builds.
- Point Bazel's Windows MSVC targets at the sandbox-enabled Codex artifacts and
  enable the matching crate feature.

## Testing

Add a runtime test that calls `v8__V8__IsSandboxEnabled()` and verifies that
the linked V8 library has sandbox support enabled.

GitOrigin-RevId: c1b49b44a6ccfea5b5006d69ec7866848d1cddd7

codex-rs/code-mode-runtime/Cargo.toml

@@ -9,9 +9,6 @@ doctest = false
 name = "codex_code_mode_runtime"
 path = "src/lib.rs"
 
-[features]
-sandbox = ["v8/v8_enable_sandbox"]
-
 [lints]
 workspace = true
 
@@ -24,7 +21,7 @@ serde_json = { workspace = true }
 tokio = { workspace = true, features = ["macros", "rt", "sync", "time"] }
 tokio-util = { workspace = true, features = ["rt"] }
 tracing = { workspace = true }
-v8 = { workspace = true }
+v8 = { workspace = true, features = ["v8_enable_sandbox"] }
 
 [dev-dependencies]
 pretty_assertions = { workspace = true }

codex-rs/code-mode-runtime/src/runtime/mod.rs

@@ -354,6 +354,19 @@ mod tests {
         }
     }
 
+    #[test]
+    fn linked_v8_has_sandbox_enabled() {
+        unsafe extern "C" {
+            fn v8__V8__IsSandboxEnabled() -> bool;
+        }
+
+        // `rusty_v8` exposes this symbol for verifying linked sandbox support.
+        assert!(
+            unsafe { v8__V8__IsSandboxEnabled() },
+            "code mode must link against sandbox-enabled V8"
+        );
+    }
+
     #[tokio::test]
     async fn runtime_thread_panic_before_initialization_is_reported_directly() {
         let (event_tx, event_rx) = mpsc::unbounded_channel();