[plugins] Add a flag for tool search. (#15722)

- [x] Add a flag for tool search.

codex-rs/features/src/lib.rs

@@ -142,6 +142,8 @@ pub enum Feature {
     SpawnCsv,
     /// Enable apps.
     Apps,
+    /// Enable the tool_search tool for apps.
+    ToolSearch,
     /// Enable discoverable tool suggestions for apps.
     ToolSuggest,
     /// Enable plugins.
@@ -717,6 +719,12 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::Stable,
         default_enabled: true,
     },
+    FeatureSpec {
+        id: Feature::ToolSearch,
+        key: "tool_search",
+        stage: Stage::UnderDevelopment,
+        default_enabled: false,
+    },
     FeatureSpec {
         id: Feature::ToolSuggest,
         key: "tool_suggest",