[codex] nest sleep config under current time reminder (#29910)

## Summary

- move sleep tool enablement from top-level `[features].sleep_tool` to
`[features.current_time_reminder].sleep_tool`
- remove the standalone `Feature::SleepTool` flag and gate `clock.sleep`
from resolved current-time configuration
- update config schema, config-lock materialization, and existing sleep
coverage

Stacked on #29907.

codex-rs/core/src/tools/spec_plan.rs

@@ -744,10 +744,14 @@ fn add_core_utility_tools(context: &CoreToolPlanContext<'_>, planned_tools: &mut
 
     if features.enabled(Feature::CurrentTimeReminder) {
         planned_tools.add(CurrentTimeHandler);
-    }
-
-    if features.enabled(Feature::SleepTool) {
-        planned_tools.add(SleepHandler);
+        if turn_context
+            .config
+            .current_time_reminder
+            .as_ref()
+            .is_some_and(|config| config.sleep_tool)
+        {
+            planned_tools.add(SleepHandler);
+        }
     }
 
     if tool_suggest_enabled(turn_context)

codex-rs/core/src/tools/spec_plan_tests.rs

@@ -31,6 +31,7 @@ use codex_tools::ToolSpec;
 use pretty_assertions::assert_eq;
 use serde_json::json;
 
+use crate::config::CurrentTimeReminderConfig;
 use crate::session::step_context::StepContext;
 use crate::session::tests::make_session_and_context;
 use crate::session::turn_context::TurnContext;
@@ -721,19 +722,27 @@ async fn host_context_gates_agent_job_tools() {
 }
 
 #[tokio::test]
-async fn sleep_tool_follows_feature_gate() {
+async fn sleep_tool_follows_current_time_config() {
     let disabled = probe(|turn| {
-        set_feature(turn, Feature::SleepTool, /*enabled*/ false);
+        set_feature(turn, Feature::CurrentTimeReminder, /*enabled*/ true);
     })
     .await;
-    disabled.assert_visible_lacks(&["clock"]);
+    assert_eq!(disabled.namespace_function_names("clock"), ["curr_time"]);
 
     let enabled = probe(|turn| {
-        set_feature(turn, Feature::SleepTool, /*enabled*/ true);
+        set_feature(turn, Feature::CurrentTimeReminder, /*enabled*/ true);
+        let mut config = (*turn.config).clone();
+        config.current_time_reminder = Some(CurrentTimeReminderConfig {
+            sleep_tool: true,
+            ..CurrentTimeReminderConfig::default()
+        });
+        turn.config = Arc::new(config);
     })
     .await;
-    enabled.assert_visible_contains(&["clock"]);
-    assert_eq!(enabled.namespace_function_names("clock"), ["sleep"]);
+    assert_eq!(
+        enabled.namespace_function_names("clock"),
+        ["curr_time", "sleep"]
+    );
 }
 
 #[tokio::test]