fix: sync lat/lng attributes on marker dragend

LeafletMarker now listens for Leaflet's 'dragend' event and writes
the final position back to the lat/lng attributes, using a #syncing
guard to prevent re-entrant setLatLng calls.

src/components/leaflet-marker.ts

@@ -25,6 +25,7 @@ const PROP_BY_ATTR = new Map<string, string>(
 
 export class LeafletMarker extends withProps(HTMLElement, PROPS) {
   #obj?: Marker;
+  #syncing = false;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
@@ -33,6 +34,7 @@ export class LeafletMarker extends withProps(HTMLElement, PROPS) {
       [this.#num('lat'), this.#num('lng')],
       buildOptions(this, PROPS, ['lat', 'lng']),
     );
+    this.#obj.on('dragend', this.#onDragEnd);
     this.#childHandler = createChildRegisterHandler(this.#obj, this.#children);
     this.addEventListener('leaflet-register', this.#childHandler);
     registerWithParent(this, this.#obj);
@@ -40,13 +42,14 @@ export class LeafletMarker extends withProps(HTMLElement, PROPS) {
 
   disconnectedCallback() {
     if (this.#childHandler) this.removeEventListener('leaflet-register', this.#childHandler);
+    this.#obj?.off('dragend', this.#onDragEnd);
     this.#children.clear();
     this.#obj?.remove();
     this.#obj = undefined;
   }
 
   attributeChangedCallback(name: string, _old: string | null, val: string | null) {
-    if (!this.#obj) return;
+    if (!this.#obj || this.#syncing) return;
     if (name === 'lat' || name === 'lng') {
       this.#obj.setLatLng([this.#num('lat'), this.#num('lng')]);
     } else {
@@ -59,6 +62,15 @@ export class LeafletMarker extends withProps(HTMLElement, PROPS) {
     }
   }
 
+  #onDragEnd = () => {
+    if (!this.#obj || this.#syncing) return;
+    this.#syncing = true;
+    const pos = this.#obj.getLatLng();
+    this.setAttribute('lat', String(pos.lat));
+    this.setAttribute('lng', String(pos.lng));
+    this.#syncing = false;
+  };
+
   #num(name: string): number {
     const v = this.getAttribute(name);
     return v !== null