Fix sidebar loading and demo (#25606)

demo/src/stubs/frontend.ts

@@ -1,7 +1,30 @@
 import type { MockHomeAssistant } from "../../../src/fake_data/provide_hass";
 
+let changeFunction;
+
 export const mockFrontend = (hass: MockHomeAssistant) => {
   hass.mockWS("frontend/get_user_data", () => ({
     value: null,
   }));
+  hass.mockWS("frontend/set_user_data", ({ key, value }) => {
+    if (key === "sidebar") {
+      changeFunction?.({
+        value: {
+          panelOrder: value.panelOrder || [],
+          hiddenPanels: value.hiddenPanels || [],
+        },
+      });
+    }
+  });
+  hass.mockWS("frontend/subscribe_user_data", (_msg, _hass, onChange) => {
+    changeFunction = onChange;
+    onChange?.({
+      value: {
+        panelOrder: [],
+        hiddenPanels: [],
+      },
+    });
+    // eslint-disable-next-line @typescript-eslint/no-empty-function
+    return () => {};
+  });
 };

src/components/ha-sidebar.ts

@@ -368,7 +368,7 @@ class HaSidebar extends SubscribeMixin(LitElement) {
     if (!this._panelOrder || !this._hiddenPanels) {
       return html`
         <ha-fade-in .delay=${500}
-          ><ha-spinner size="large"></ha-spinner
+          ><ha-spinner size="small"></ha-spinner
         ></ha-fade-in>
       `;
     }