feat: add onMemoryPlaced callback for particle system integration

nexus/components/spatial-memory.js

@@ -32,6 +32,9 @@
 
 const SpatialMemory = (() => {
 
+  // ─── CALLBACKS ────────────────────────────────────────
+  let _onMemoryPlacedCallback = null;
+
   // ─── REGION DEFINITIONS ───────────────────────────────
   const REGIONS = {
     engineering: {
@@ -301,6 +304,12 @@ const SpatialMemory = (() => {
     _dirty = true;
     saveToStorage();
     console.info('[Mnemosyne] Spatial memory placed:', mem.id, 'in', region.label);
+
+    // Fire particle burst callback
+    if (_onMemoryPlacedCallback) {
+      _onMemoryPlacedCallback(crystal.position.clone(), mem.category || 'working');
+    }
+
     return crystal;
   }
 
@@ -897,6 +906,10 @@ const SpatialMemory = (() => {
     return obj ? obj.mesh.position.clone() : null;
   }
 
+  function setOnMemoryPlaced(callback) {
+    _onMemoryPlacedCallback = callback;
+  }
+
   return {
     init, placeMemory, removeMemory, update, updateMemoryVisual,
     getMemoryAtPosition, getRegionAtPosition, getMemoriesInRegion, getAllMemories,
@@ -904,7 +917,8 @@ const SpatialMemory = (() => {
     exportIndex, importIndex, exportToFile, importFromFile, searchNearby, REGIONS,
     saveToStorage, loadFromStorage, clearStorage,
     runGravityLayout,
-    searchContent, highlightSearchResults, clearSearch, getSearchMatchPosition
+    searchContent, highlightSearchResults, clearSearch, getSearchMatchPosition,
+    setOnMemoryPlaced
   };
 })();