Add an incremental exec tools feature flag (#58122)

Register `incremental_exec_tools` as an under-development feature, disabled
by default, and expose it in the configuration schema.

GitOrigin-RevId: 444767b7a46e3ada7efb3f6c4fb570feb299e0c7

codex-rs/core/config.schema.json

@@ -1122,6 +1122,9 @@
             "in_app_voice": {
               "type": "boolean"
             },
+            "incremental_exec_tools": {
+              "type": "boolean"
+            },
             "incremental_tools": {
               "type": "boolean"
             },
@@ -7784,6 +7787,9 @@
         "in_app_voice": {
           "type": "boolean"
         },
+        "incremental_exec_tools": {
+          "type": "boolean"
+        },
         "incremental_tools": {
           "type": "boolean"
         },

codex-rs/features/src/lib.rs

@@ -293,6 +293,8 @@ pub enum Feature {
     IncrementalTools,
     /// Preserve inherited tool declarations in MCP-disabled prediction forks.
     PredictionPreserveParentTools,
+    /// Diff CodeModeOnly exec definitions within the incremental tool catalog.
+    IncrementalExecTools,
     /// Expose MCP model-visible namespaces without the legacy `mcp__` prefix.
     NonPrefixedMcpToolNames,
     /// Enable discoverable tool suggestions for apps.
@@ -1727,6 +1729,12 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::Stable,
         default_enabled: true,
     },
+    FeatureSpec {
+        id: Feature::IncrementalExecTools,
+        key: "incremental_exec_tools",
+        stage: Stage::UnderDevelopment,
+        default_enabled: false,
+    },
     FeatureSpec {
         id: Feature::NonPrefixedMcpToolNames,
         key: "non_prefixed_mcp_tool_names",