3D Mobile Offline Write-Queue Relay Simulator

Same ordered-queue idea as the 2D simulator, but the drain now has to pass through two independently versioned checkpoints instead of one: a device on the left queues writes offline, an edge cache sits in the middle, and the origin server sits on the right. Each queued op travels device → edge → origin in strict FIFO order, and it can be rejected at either hop if that node's version has moved since the op was queued — for example when "Write @ Origin" lets the origin drift ahead of what the edge (and the device) still believe is current. Orbit the scene, pick a conflict policy, and drain the queue to see exactly which hop stops an op and why.