Select the elevated Windows sandbox for network proxies (#33445)

## Why

Windows firewall enforcement is tied to the logon-user sandbox identities. Proxy-enforced commands therefore need the elevated backend even when the configured sandbox mode is the default restricted-token mode.

## What changed

- Select the elevated Windows sandbox backend whenever a command uses the managed network proxy.
- Remove configuration and startup checks that required users or managed requirements to select the elevated sandbox explicitly.
- Start and expose managed network proxy state consistently on Windows.

## Testing

- Verify that proxy enforcement selects the elevated backend for the restricted-token sandbox mode.

GitOrigin-RevId: e01ac052587721c468a8fbcf4e2c7c5a185a3e05

codex-rs/app-server/src/request_processors/command_exec_processor.rs

@@ -204,7 +204,6 @@ impl CommandExecRequestProcessor {
             network_proxy_permission_profile,
             managed_network_requirements_enabled,
             windows_sandbox_workspace_roots,
-            windows_sandbox_level,
         ) = if let Some(permission_profile) = permission_profile {
             let overrides = ConfigOverrides {
                 cwd: Some(cwd.to_path_buf()),
@@ -233,7 +232,6 @@ impl CommandExecRequestProcessor {
                 config.permissions.permission_profile().clone(),
                 config.managed_network_requirements_enabled(),
                 config.effective_workspace_roots(),
-                WindowsSandboxLevel::from_config(&config),
             )
         } else if let Some(policy) = sandbox_policy.map(|policy| policy.to_core()) {
             self.config
@@ -260,7 +258,6 @@ impl CommandExecRequestProcessor {
                 self.config.permissions.permission_profile().clone(),
                 self.config.managed_network_requirements_enabled(),
                 self.config.effective_workspace_roots(),
-                windows_sandbox_level,
             )
         } else {
             (
@@ -269,13 +266,9 @@ impl CommandExecRequestProcessor {
                 self.config.permissions.permission_profile().clone(),
                 self.config.managed_network_requirements_enabled(),
                 self.config.effective_workspace_roots(),
-                windows_sandbox_level,
             )
         };
-        let started_network_proxy = match network_proxy_spec
-            .as_ref()
-            .filter(|spec| !cfg!(target_os = "windows") || spec.enabled())
-        {
+        let started_network_proxy = match network_proxy_spec.as_ref() {
             Some(spec) => match spec
                 .start_proxy(
                     &network_proxy_permission_profile,

codex-rs/app-server/src/request_processors/windows_sandbox_processor.rs

@@ -63,19 +63,6 @@ impl WindowsSandboxRequestProcessor {
             config.config_layer_stack.requirements(),
             params.mode,
         )?;
-        let target_windows_sandbox_level = match setup_mode {
-            CoreWindowsSandboxSetupMode::Elevated => WindowsSandboxLevel::Elevated,
-            CoreWindowsSandboxSetupMode::Unelevated => WindowsSandboxLevel::RestrictedToken,
-        };
-        codex_core::config::validate_windows_sandbox_network_proxy_compatibility(
-            target_windows_sandbox_level,
-            config
-                .permissions
-                .network
-                .as_ref()
-                .is_some_and(codex_core::config::NetworkProxySpec::enabled),
-        )
-        .map_err(|err| invalid_request(err.to_string()))?;
 
         self.outgoing
             .send_response(