feat: add mixer scene API methods to PiPedalModel

vite/src/pipedal/PiPedalModel.tsx

@@ -3986,6 +3986,39 @@ export class PiPedalModel //implements PiPedalModel
         );
     }
 
+    // -------------------------------------------------------------------------
+    // Mixer Scene Management
+    // -------------------------------------------------------------------------
+
+    /**
+     * Get the full mixer state as a JSON string.
+     */
+    async getMixerState(): Promise<string> {
+        return await this.getWebSocket().request<string>("mixerGetState");
+    }
+
+    /**
+     * Save the current mixer state as a named scene.
+     * Returns {id, name} from the backend.
+     */
+    async saveMixerScene(name: string): Promise<{ id: number; name: string }> {
+        return await this.getWebSocket().request<{ id: number; name: string }>("mixerSaveScene", { name });
+    }
+
+    /**
+     * Load a scene by its backend ID. Returns true on success.
+     */
+    async loadMixerScene(sceneId: number): Promise<boolean> {
+        return await this.getWebSocket().request<boolean>("mixerLoadScene", { sceneId });
+    }
+
+    /**
+     * Get list of saved scenes from backend. Returns raw JSON string.
+     */
+    async getMixerScenes(): Promise<string> {
+        return await this.getWebSocket().request<string>("mixerGetScenes");
+    }
+
 };
 
 let instance: PiPedalModel | undefined = undefined;