fix: motion-responsive skeleton + through-wall CSI tracking

- Pose decoder now uses per-cell motion grid to track actual arm/head
  positions — raising arms moves the skeleton's arms, head follows
  lateral movement
- Motion grid (10x8 cells) tracks intensity per body zone: head,
  left/right arm upper/mid, legs
- Through-wall mode: when person exits frame, CSI maintains presence
  with slow decay (~10s) and skeleton drifts in exit direction
- CSI simulator persists sensing after video loss, ghost pose renders
  with decreasing confidence
- Reduced temporal smoothing (0.45) for faster response to movement

Co-Authored-By: claude-flow <ruv@ruv.net>

ui/pose-fusion/js/csi-simulator.js

@@ -68,13 +68,38 @@ export class CsiSimulator {
   get isLive() { return this.mode === 'live'; }
 
   /**
-   * Update person state from video detection (for correlated demo data)
+   * Update person state from video detection (for correlated demo data).
+   * When person exits frame, CSI maintains presence with slow decay
+   * (simulating through-wall sensing capability).
    */
   updatePersonState(presence, x, y, motion) {
-    this.personPresence = presence;
-    this.personX = x;
-    this.personY = y;
-    this.personMotion = motion;
+    if (presence > 0.1) {
+      // Person detected in video — update CSI state directly
+      this.personPresence = presence;
+      this.personX = x;
+      this.personY = y;
+      this.personMotion = motion;
+      this._lastSeenTime = performance.now();
+      this._lastSeenX = x;
+      this._lastSeenY = y;
+    } else if (this._lastSeenTime) {
+      // Person NOT in video — CSI "through-wall" persistence
+      const elapsed = (performance.now() - this._lastSeenTime) / 1000;
+      // CSI can sense through walls for ~10 seconds with decaying confidence
+      const decayRate = 0.15; // Lose ~15% per second
+      this.personPresence = Math.max(0, 1.0 - elapsed * decayRate);
+      // Position slowly drifts (person walking behind wall)
+      this.personX = this._lastSeenX;
+      this.personY = this._lastSeenY;
+      this.personMotion = Math.max(0, motion * 0.5 + this.personPresence * 0.2);
+
+      if (this.personPresence < 0.05) {
+        this._lastSeenTime = null;
+      }
+    } else {
+      this.personPresence = 0;
+      this.personMotion = 0;
+    }
   }
 
   /**