Add standalone POC comparing WebRTC DataChannel vs Socket.IO

Self-contained test under poc-webrtc/ that does not touch the game.
Spins up an Express + WebSocket signaling + node-datachannel server
alongside a Socket.IO server, serves a simple browser client that
runs the same game-like traffic pattern (14Hz worldUpdates, input
events, ping/pong) over either transport based on a URL flag.

Captures per-session stats to a JSONL file and ships an analyze.js
that prints a per-(transport, phase) summary of RTT percentiles,
receive rate, and seq-gap counts so the TCP-vs-UDP-style comparison
becomes quantitative rather than eyeball.

Confirms node-datachannel installs and works on this platform and
that the dual-channel (reliable + unreliable) pattern is feasible
to maintain — both prerequisites for the real integration.

poc-webrtc/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "chuck-webrtc-poc",
+  "version": "0.0.1",
+  "description": "POC: WebRTC DataChannel vs Socket.IO for chuck.js networking",
+  "main": "server.js",
+  "private": true,
+  "scripts": {
+    "start": "node server.js"
+  },
+  "dependencies": {
+    "express": "^4.18.2",
+    "node-datachannel": "^0.10.0",
+    "socket.io": "^4.7.4",
+    "ws": "^8.16.0"
+  }
+}