Replace cheat-detection teleport with server reconciliation

The old PUNKBUSTER check compared client-reported position to server
position and snapped the player back when latency made them diverge,
which felt like getting teleported under any real network conditions.

Replaces that with proper client-side prediction + reconciliation:
client tags each input with a sequence number and keeps an input
buffer; server tracks the last processed sequence and reports its
authoritative position via a per-user inputAck alongside each
worldUpdate. The client only corrects when the actual disagreement
exceeds what the unacked input time can explain — so steady-state
movement runs purely on local physics, and only genuine unexpected
events (collisions, being hit) trigger a smooth blend toward the
server state.

Includes adaptive threshold scaling so high-latency sessions don't
false-positive corrections during normal running.

.gitignore

@@ -5,3 +5,6 @@ lab/audio/
 lab/filter/
 static/items/rube/*-backups
 build/
+runs/
+poc-webrtc/runs/
+poc-webrtc/node_modules/