Remove server reconciliation in favor of pure client prediction

The reconciliation system caused visible teleportation at high latency
(e.g. 250ms Germany→Korea): position corrections snapped the local
player and thrown items back to stale server states.

- Drop the inputAck/seq tracking, InputBuffer, and applyReconciliation.
  The client predicts locally and the server stays authoritative via
  the existing worldUpdate broadcast; own-doll updates remain ignored.
- Override Item.setUpdateData on the client so in-flight items run free
  on local Box2D physics (client and server share the same throw
  impulse) and only sync when stationary or far out of sync. This keeps
  grab-sensor contact accurate while eliminating mid-flight snapping.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/Game/Client/GameObjects/Item.js

@@ -19,7 +19,30 @@ function (Parent, Settings, nc, Layer) {
     }
 
     Item.prototype = Object.create(Parent.prototype);
- 
+
+    Item.prototype.setUpdateData = function(update) {
+        var currentPos = this.body.GetPosition();
+        var diffX = update.p.x - currentPos.x;
+        var diffY = update.p.y - currentPos.y;
+        var distance = Math.sqrt(diffX * diffX + diffY * diffY);
+        var speed = Math.sqrt(update.lv.x * update.lv.x + update.lv.y * update.lv.y);
+
+        this.body.SetAwake(true);
+
+        if (distance > 3 || speed < 0.5) {
+            // Stationary: sync so grab sensor contact is accurate.
+            // Large error: snap for respawn/warp/grab events.
+            this.body.SetPosition(update.p);
+            this.body.SetAngle(update.a);
+            this.body.SetLinearVelocity(update.lv);
+            this.body.SetAngularVelocity(update.av);
+        }
+        // In-flight: skip correction entirely. Client and server both run the
+        // same Box2D physics from the same throw impulse, so they stay close
+        // without per-update snapping. Applying the server's stale state would
+        // snap the item back to where it was 125 ms ago.
+    };
+
     Item.prototype.createMesh = function() {
     	var self = this;