Fix cytoscapeStore: preserve positions, guard access, remove redundant write

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/stores/cytoscapeStore.ts

@@ -64,7 +64,6 @@ export const useCytoscapeStore = defineStore('cytoscapeStore', {
       } else {
         this.nodePositions[this.currentGraphId][direction]
           .push({ id: nodeId, position: position });
-        localStorage.setItem(SAVE_KEY_NAME, JSON.stringify(this.nodePositions));
       }
       this.savePositionsToStorage();
     },
@@ -73,6 +72,7 @@ export const useCytoscapeStore = defineStore('cytoscapeStore', {
      * @param {string} direction - Layout direction ('TB' or 'LR').
      */
     loadPositionsFromStorage(direction: string) {
+      if (!this.nodePositions[this.currentGraphId]) return;
       try {
         const raw = localStorage.getItem(SAVE_KEY_NAME);
         if (raw) {
@@ -94,12 +94,9 @@ export const useCytoscapeStore = defineStore('cytoscapeStore', {
     },
     setCurrentGraphId(currentGraphId: string) {
       this.currentGraphId = currentGraphId;
-      this.nodePositions = {
-        [this.currentGraphId]: {
-          'TB': [],
-          'LR': [],
-        }
-      };
+      if (!this.nodePositions[currentGraphId]) {
+        this.nodePositions[currentGraphId] = { TB: [], LR: [] };
+      }
     },
   },
 });