Windows Sandbox - Alpha version (#4905)

- Added the new codex-windows-sandbox crate that builds both a library
entry point (run_windows_sandbox_capture) and a CLI executable to launch
commands inside a Windows restricted-token sandbox, including ACL
management, capability SID provisioning, network lockdown, and output
capture
(windows-sandbox-rs/src/lib.rs:167, windows-sandbox-rs/src/main.rs:54).
- Introduced the experimental WindowsSandbox feature flag and wiring so
Windows builds can opt into the sandbox:
SandboxType::WindowsRestrictedToken, the in-process execution path, and
platform sandbox selection now honor the flag (core/src/features.rs:47,
core/src/config.rs:1224, core/src/safety.rs:19,
core/src/sandboxing/mod.rs:69, core/src/exec.rs:79,
core/src/exec.rs:172).
- Updated workspace metadata to include the new crate and its
Windows-specific dependencies so the core crate can link against it
(codex-rs/
    Cargo.toml:91, core/Cargo.toml:86).
- Added a PowerShell bootstrap script that installs the Windows
toolchain, required CLI utilities, and builds the workspace to ease
development
    on the platform (scripts/setup-windows.ps1:1).
- Landed a Python smoke-test suite that exercises
read-only/workspace-write policies, ACL behavior, and network denial for
the Windows sandbox
    binary (windows-sandbox-rs/sandbox_smoketests.py:1).

codex-rs/windows-sandbox-rs/src/cap.rs

@@ -0,0 +1,50 @@
+use rand::rngs::SmallRng;
+use rand::RngCore;
+use rand::SeedableRng;
+use serde::Deserialize;
+use serde::Serialize;
+use std::fs;
+use std::path::Path;
+use std::path::PathBuf;
+
+#[derive(Serialize, Deserialize, Clone, Debug)]
+pub struct CapSids {
+    pub workspace: String,
+    pub readonly: String,
+}
+
+pub fn cap_sid_file(policy_cwd: &Path) -> PathBuf {
+    policy_cwd.join(".codex").join("cap_sid")
+}
+
+fn make_random_cap_sid_string() -> String {
+    let mut rng = SmallRng::from_entropy();
+    let a = rng.next_u32();
+    let b = rng.next_u32();
+    let c = rng.next_u32();
+    let d = rng.next_u32();
+    format!("S-1-5-21-{}-{}-{}-{}", a, b, c, d)
+}
+
+pub fn load_or_create_cap_sids(policy_cwd: &Path) -> CapSids {
+    let path = cap_sid_file(policy_cwd);
+    if path.exists() {
+        if let Ok(txt) = fs::read_to_string(&path) {
+            let t = txt.trim();
+            if t.starts_with('{') && t.ends_with('}') {
+                if let Ok(obj) = serde_json::from_str::<CapSids>(t) {
+                    return obj;
+                }
+            } else if !t.is_empty() {
+                return CapSids {
+                    workspace: t.to_string(),
+                    readonly: make_random_cap_sid_string(),
+                };
+            }
+        }
+    }
+    CapSids {
+        workspace: make_random_cap_sid_string(),
+        readonly: make_random_cap_sid_string(),
+    }
+}