[Codex] Register browser requirements feature keys (#18956)

## Summary
- register `in_app_browser` and `browser_use` as stable feature keys
- allow requirements/MDM feature requirements to pin those desktop
browser controls
- add coverage for browser requirements being accepted by config loading

## Testing
- `cargo fmt --all` (`just fmt` unavailable locally; rustfmt warned
about nightly-only `imports_granularity` config)
- `cargo test -p codex-features`
- `cargo test -p codex-core browser_feature_requirements_are_valid`
- Tested manually by setting in `requirements.toml` and seeing after app
restart state to reflect the setting was correct (at the time hiding the
`Browser Use` setting when the enterprise setting was set to false

codex-rs/features/src/lib.rs

@@ -156,6 +156,14 @@ pub enum Feature {
     ToolSuggest,
     /// Enable plugins.
     Plugins,
+    /// Allow the in-app browser pane in desktop apps.
+    ///
+    /// Requirements-only gate: this should be set from requirements, not user config.
+    InAppBrowser,
+    /// Allow Browser Use agent integration in desktop apps.
+    ///
+    /// Requirements-only gate: this should be set from requirements, not user config.
+    BrowserUse,
     /// Temporary internal-only flag for PS-backed remote plugin catalog development.
     RemotePlugin,
     /// Show the startup prompt for migrating external agent config into Codex.
@@ -848,6 +856,18 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::Stable,
         default_enabled: true,
     },
+    FeatureSpec {
+        id: Feature::InAppBrowser,
+        key: "in_app_browser",
+        stage: Stage::Stable,
+        default_enabled: true,
+    },
+    FeatureSpec {
+        id: Feature::BrowserUse,
+        key: "browser_use",
+        stage: Stage::Stable,
+        default_enabled: true,
+    },
     FeatureSpec {
         id: Feature::RemotePlugin,
         key: "remote_plugin",

codex-rs/features/src/tests.rs

@@ -150,6 +150,20 @@ fn tool_search_is_stable_and_enabled_by_default() {
     assert_eq!(Feature::ToolSearch.default_enabled(), true);
 }
 
+#[test]
+fn browser_controls_are_stable_and_enabled_by_default() {
+    assert_eq!(Feature::InAppBrowser.stage(), Stage::Stable);
+    assert_eq!(Feature::InAppBrowser.default_enabled(), true);
+    assert_eq!(
+        feature_for_key("in_app_browser"),
+        Some(Feature::InAppBrowser)
+    );
+
+    assert_eq!(Feature::BrowserUse.stage(), Stage::Stable);
+    assert_eq!(Feature::BrowserUse.default_enabled(), true);
+    assert_eq!(feature_for_key("browser_use"), Some(Feature::BrowserUse));
+}
+
 #[test]
 fn unavailable_dummy_tools_is_under_development_and_disabled_by_default() {
     assert_eq!(