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/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>,