Add PDF state persistence

src-tauri/assets/viewer/message-bridge.js

@@ -18,6 +18,17 @@ export class MessageBridge {
     window.addEventListener("message", this._handler);
   }
 
+  /** Send the current viewer state (zoom + scroll) to the parent window. */
+  postViewerState(refId, zoom, scrollTop) {
+    if (window.parent === window) return;
+    window.parent.postMessage({
+      type: "brittle:viewer-state",
+      refId,
+      zoom,
+      scrollTop,
+    }, "*");
+  }
+
   /** Forward a keydown event to the parent window for global keybindings. */
   forwardKeydown(ev) {
     if (window.parent === window) return;