UiService v2.1: Virtualized lists (#2342)

* UiService: Add `pane_add_list`

* Fix CSS scoping

docs/modding.md

@@ -496,6 +496,49 @@ controls are only available inside window tabs.
 and calls the group's build callback with that pane, which is useful for organizing related controls without adding
 more tabs.
 
+**Lists:** `pane_add_list` adds a scrollable virtualized list of items that can be efficiently updated and filtered.
+Keys must be unique and remain stable across replacements.
+
+```cpp
+UiListHandle locationList = 0;
+
+void replace_locations(std::string_view query) {
+    std::vector<UiListItem> items;
+    for (uint64_t i = 0; i < locations.size(); ++i) {
+        if (matches(locations[i], query)) {
+            UiListItem item = UI_LIST_ITEM_INIT;
+            item.key = i;
+            item.label = locations[i].c_str();
+            items.push_back(item);
+        }
+    }
+    svc_ui->list_set_items(mod_ctx, locationList, items.data(), items.size());
+}
+
+void set_filter(ModContext*, void*, const UiControlValue* value) {
+    replace_locations(value->string_value);
+}
+
+bool location_selected(ModContext*, UiListHandle, uint64_t key, void*) {
+    return selected_locations.contains(key);
+}
+
+UiControlDesc filter = UI_CONTROL_DESC_INIT;
+filter.kind = UI_CONTROL_STRING;
+filter.label = "Filter";
+filter.get = get_filter;
+filter.set = set_filter;
+filter.string_set_mode = UI_STRING_SET_ON_CHANGE; /* invoke `set` while typing */
+svc_ui->pane_add_control(mod_ctx, pane, &filter, nullptr);
+
+UiListDesc list = UI_LIST_DESC_INIT;
+/* items may be passed as a part of list creation, or set afterwards */
+list.on_pressed = location_pressed;
+list.is_selected = location_selected;
+svc_ui->pane_add_list(mod_ctx, pane, &list, &locationList);
+replace_locations(""); /* calls `list_set_items` */
+```
+
 **Windows:** `window_push` pushes a tabbed two-pane window onto the document stack and shows it. Each tab's `build`
 receives the window handle plus fresh left and right pane handles on every activation. The optional per-tab `update`
 runs each frame while that tab is active. `on_closed` fires when the window is destroyed. `desc.rcss` optionally styles