Add managed gates for in-app chat and dictation (#39045)

## What changed

- Register `in_app_chat` and `in_app_dictation` as stable, default-enabled feature gates for desktop apps.
- Allow requirements to disable either capability and expose both keys in the generated configuration schema.

## Testing

- Add configuration tests that verify enterprise requirements can disable each gate.

GitOrigin-RevId: 5bba35d710fb0b6924aa55df98b2e013fa288f6d

codex-rs/features/src/lib.rs

@@ -206,6 +206,14 @@ pub enum Feature {
     ///
     /// Requirements-only gate: this should be set from requirements, not user config.
     InAppBrowser,
+    /// Allow the in-app chat pane in desktop apps.
+    ///
+    /// Requirements-only gate: this should be set from requirements, not user config.
+    InAppChat,
+    /// Allow in-app dictation in desktop apps.
+    ///
+    /// Requirements-only gate: this should be set from requirements, not user config.
+    InAppDictation,
     /// Allow desktop apps to perform in-app updates.
     ///
     /// Requirements-only gate: this should be set from requirements, not user config.
@@ -1210,6 +1218,18 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::Stable,
         default_enabled: true,
     },
+    FeatureSpec {
+        id: Feature::InAppChat,
+        key: "in_app_chat",
+        stage: Stage::Stable,
+        default_enabled: true,
+    },
+    FeatureSpec {
+        id: Feature::InAppDictation,
+        key: "in_app_dictation",
+        stage: Stage::Stable,
+        default_enabled: true,
+    },
     FeatureSpec {
         id: Feature::InAppUpdates,
         key: "in_app_updates",