[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/config.schema.json

@@ -643,9 +643,6 @@
             "skill_mcp_dependency_install": {
               "type": "boolean"
             },
-            "sleep_tool": {
-              "type": "boolean"
-            },
             "sqlite": {
               "type": "boolean"
             },
@@ -820,6 +817,10 @@
           "format": "uint64",
           "minimum": 1.0,
           "type": "integer"
+        },
+        "sleep_tool": {
+          "description": "Expose the input-interruptible `clock.sleep` tool.",
+          "type": "boolean"
         }
       },
       "type": "object"
@@ -4951,9 +4952,6 @@
         "skill_mcp_dependency_install": {
           "type": "boolean"
         },
-        "sleep_tool": {
-          "type": "boolean"
-        },
         "sqlite": {
           "type": "boolean"
         },