Add Multiplayer (PartyKit / Cloudflare Durable Objects)

Add real-time or turn-based multiplayer to an existing single-player browser game. This skill scaffolds:

1. A PartyKit server (one Durable Object per room) deployed to Cloudflare's edge.
2. A client NetworkManager wired through EventBus that mirrors the existing playfun.js external-service pattern.
3. Additive edits to EventBus, GameState, Constants, and render_game_to_text() — single-player gameplay must remain identical when the server is unreachable.

The default state is "single-player works." If the WebSocket connection fails, NetworkManager swallows the error and the game runs locally as before. When connected, remote players appear via network:player-joined and synchronize via network:state-received.

Reference Files

• architecture.md — event taxonomy, GameState schema, NetworkManager contract, Phaser vs Three.js placement notes.
• partykit-server.md — server templates (realtime.ts and turn-based.ts), state shape, broadcast helpers, rate limiting.
• client-integration.md — MultiplayerClient, NetworkManager, RemotePlayerRegistry source, EventBus/GameState/Constants append patterns, render_game_to_text extension.
• deploy.md — npx partykit dev and npx partykit deploy walkthrough, capturing the deployed URL, .env handling, and client redeploy.

Core Principles