[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/features/src/feature_configs.rs

@@ -147,6 +147,9 @@ pub struct CurrentTimeReminderConfigToml {
     pub reminder_interval_seconds: Option<u64>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub clock_source: Option<CurrentTimeSource>,
+    /// Expose the input-interruptible `clock.sleep` tool.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub sleep_tool: Option<bool>,
 }
 
 impl FeatureConfig for CurrentTimeReminderConfigToml {

codex-rs/features/src/lib.rs

@@ -219,8 +219,6 @@ pub enum Feature {
     RolloutBudget,
     /// Add current-time reminders to model-visible context.
     CurrentTimeReminder,
-    /// Expose an input-interruptible sleep tool.
-    SleepTool,
     /// Route MCP tool approval prompts through the MCP elicitation request path.
     ToolCallMcpElicitation,
     /// Prompt Codex Apps connector auth failures through MCP URL elicitations.
@@ -1243,12 +1241,6 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::UnderDevelopment,
         default_enabled: false,
     },
-    FeatureSpec {
-        id: Feature::SleepTool,
-        key: "sleep_tool",
-        stage: Stage::UnderDevelopment,
-        default_enabled: false,
-    },
     FeatureSpec {
         id: Feature::CollaborationModes,
         key: "collaboration_modes",