Move sleep items to the extension-owned lifecycle path (#33159)

## What changed

- Define `SleepItem` in `codex-extension-items` and carry `clock.sleep` events through `TurnItem::Extension`.
- Preserve sleep persistence, thread-history reconstruction, and the app-server's `type: "sleep"` schema while reusing the extension-owned type.

## Testing

- Add serialization coverage for the `clock.sleep` extension wire shape and its protocol wrapper.
- Update sleep lifecycle and thread-history tests to exercise the extension-owned item.

GitOrigin-RevId: 34bb33ed9b90a09bf4744aafdb56e019c717a168

codex-rs/app-server-protocol/src/protocol/v2/item.rs

@@ -14,6 +14,7 @@ use crate::protocol::item_builders::review_output_text;
 use codex_experimental_api_macros::ExperimentalApi;
 use codex_extension_items::ExtensionItem;
 pub use codex_extension_items::image_generation::ImageGenerationItem;
+pub use codex_extension_items::sleep::SleepItem;
 pub use codex_extension_items::web_search::WebSearchAction;
 pub use codex_extension_items::web_search::WebSearchItem;
 use codex_protocol::approvals::GuardianAssessmentAction as CoreGuardianAssessmentAction;
@@ -368,13 +369,7 @@ pub enum ThreadItem {
         id: String,
         path: LegacyAppPathString,
     },
-    #[serde(rename_all = "camelCase")]
-    #[ts(rename_all = "camelCase")]
-    Sleep {
-        id: String,
-        #[ts(type = "number")]
-        duration_ms: u64,
-    },
+    Sleep(SleepItem),
     ImageGeneration(ImageGenerationItem),
     #[serde(rename_all = "camelCase")]
     #[ts(rename_all = "camelCase")]
@@ -430,11 +425,11 @@ impl ThreadItem {
             | ThreadItem::CollabAgentToolCall { id, .. }
             | ThreadItem::SubAgentActivity { id, .. }
             | ThreadItem::ImageView { id, .. }
-            | ThreadItem::Sleep { id, .. }
             | ThreadItem::EnteredReviewMode { id, .. }
             | ThreadItem::ExitedReviewMode { id, .. }
             | ThreadItem::ContextCompaction { id, .. } => id,
             ThreadItem::WebSearch(item) => &item.id,
+            ThreadItem::Sleep(item) => &item.id,
             ThreadItem::ImageGeneration(item) => &item.id,
         }
     }
@@ -908,12 +903,9 @@ impl From<CoreTurnItem> for ThreadItem {
                 id: image.id,
                 path: image.path.into(),
             },
-            CoreTurnItem::Sleep(sleep) => ThreadItem::Sleep {
-                id: sleep.id,
-                duration_ms: sleep.duration_ms,
-            },
             CoreTurnItem::Extension(extension) => match extension {
                 ExtensionItem::ImageGeneration(item) => ThreadItem::ImageGeneration(item),
+                ExtensionItem::Sleep(item) => ThreadItem::Sleep(item),
                 ExtensionItem::WebSearch(item) => ThreadItem::WebSearch(item),
             },
             CoreTurnItem::ImageGeneration(image) => {