Support paginated thread history in app-server list APIs (#33152)

## Why

Clients could discover threads with paginated history, but could not page their
turns through `thread/turns/list`.

## What changed

- Route `thread/turns/list` for paginated threads through the thread store,
  preserving cursors, sort direction, turn status, timing, errors, and the
  requested `summary` or `notLoaded` item view.
- Reject the `full` turn item view for paginated threads and direct clients to
  `thread/items/list` for complete item pagination.
- Return each item page entry with both its containing `turnId` and `item`, so
  clients can regroup thread-wide pages into turns.
- Expose local thread-store turn and item pagination through the `ThreadStore`
  implementation.

## Testing

Added app-server coverage for paging projected turns and items, item views,
cursors, turn metadata, and rejection of the unsupported `full` view.

GitOrigin-RevId: 9c4a127a9b4fa91313f0e87494c62fe2e3a06f19

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

@@ -256,8 +256,11 @@ fn thread_items_list_round_trips() {
         })
     );
     let response = ThreadItemsListResponse {
-        data: vec![ThreadItem::ContextCompaction {
-            id: "item_1".to_string(),
+        data: vec![ThreadItemEntry {
+            turn_id: "turn_456".to_string(),
+            item: ThreadItem::ContextCompaction {
+                id: "item_1".to_string(),
+            },
         }],
         next_cursor: None,
         backwards_cursor: Some("cursor_0".to_string()),
@@ -266,7 +269,10 @@ fn thread_items_list_round_trips() {
     assert_eq!(
         serde_json::to_value(&response).expect("serialize response"),
         json!({
-            "data": [{"type": "contextCompaction", "id": "item_1"}],
+            "data": [{
+                "turnId": "turn_456",
+                "item": {"type": "contextCompaction", "id": "item_1"},
+            }],
             "nextCursor": null,
             "backwardsCursor": "cursor_0",
         })

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

@@ -1353,11 +1353,20 @@ pub struct ThreadItemsListParams {
     pub sort_direction: Option<SortDirection>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadItemEntry {
+    /// Turn containing this item.
+    pub turn_id: String,
+    pub item: ThreadItem,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]
 pub struct ThreadItemsListResponse {
-    pub data: Vec<ThreadItem>,
+    pub data: Vec<ThreadItemEntry>,
     /// Opaque cursor to pass to the next call to continue after the last item.
     /// if None, there are no more items to return.
     pub next_cursor: Option<String>,