feat(mnemosyne): integrate ambient particle system into Nexus

- Import MemoryParticles component
- Init after SpatialMemory, wire onMemoryPlaced callback
- Update in animation loop
- Spawn burst on memory placement (via callback)
- Access trail on crystal click and navigate
- Category colors for all particles

app.js

@@ -8,6 +8,7 @@ import { SMAAPass } from 'three/addons/postprocessing/SMAAPass.js';
 import { SpatialMemory } from './nexus/components/spatial-memory.js';
 import { SessionRooms } from './nexus/components/session-rooms.js';
 import { TimelineScrubber } from './nexus/components/timeline-scrubber.js';
+import { MemoryParticles } from './nexus/components/memory-particles.js';
 
 // ═══════════════════════════════════════════
 // NEXUS v1.1 — Portal System Update
@@ -709,6 +710,8 @@ async function init() {
   createWorkshopTerminal();
   createAshStorm();
   SpatialMemory.init(scene);
+  MemoryParticles.init(scene);
+  SpatialMemory.setOnMemoryPlaced(MemoryParticles.onMemoryPlaced);
   TimelineScrubber.init(SpatialMemory);
   SessionRooms.init(scene, camera, null);
   updateLoad(90);
@@ -1915,6 +1918,10 @@ function setupControls() {
             const memInfo = SpatialMemory.getMemoryFromMesh(hitMesh);
             if (memInfo) {
               SpatialMemory.highlightMemory(memInfo.data.id);
+              // Memory access trail particles
+              if (camera) {
+                MemoryParticles.onMemoryAccessed(camera.position, hitMesh.position, memInfo.data.category || memInfo.region || 'working');
+              }
               showMemoryPanel(memInfo, e.clientX, e.clientY);
               return;
             }
@@ -2770,6 +2777,18 @@ function _positionPanel(panel, clickX, clickY) {
 function _navigateToMemory(memId) {
   SpatialMemory.highlightMemory(memId);
   addChatMessage('system', `Focus: ${memId.replace(/_/g, ' ')}`);
+
+  // Access trail particles
+  const meshes = SpatialMemory.getCrystalMeshes();
+  for (const mesh of meshes) {
+    if (mesh.userData && mesh.userData.memId === memId) {
+      const memInfo = SpatialMemory.getMemoryFromMesh(mesh);
+      if (memInfo && camera) {
+        MemoryParticles.onMemoryAccessed(camera.position, mesh.position, memInfo.data.category || memInfo.region || 'working');
+      }
+      break;
+    }
+  }
   const meshes = SpatialMemory.getCrystalMeshes();
   for (const mesh of meshes) {
     if (mesh.userData && mesh.userData.memId === memId) {
@@ -2975,6 +2994,7 @@ function gameLoop() {
   // Project Mnemosyne - Memory Orb Animation
   if (typeof animateMemoryOrbs === 'function') {
     SpatialMemory.update(delta);
+    MemoryParticles.update(delta);
     TimelineScrubber.update();
     animateMemoryOrbs(delta);
   }