feat: Pokemon Battle World Agent + world manifest protocol

[Jing-yilin]

Summary

When an agent joins a world via world.join, the response should include a manifest describing the world rules, available actions, and objectives. This lets AI agents understand how to play without external docs.

Create a Pokemon Battle World Agent (world/pokemon.mjs) as the first game world:

• Uses @pkmn/sim + @pkmn/randoms for battle engine (MIT license)
• 1v1 battles with 3 random Gen 1 Pokemon each
• Single-player mode: agent vs built-in RandomAI
• Returns structured battle state on each turn
• Sends world manifest on join explaining rules + action format

Protocol: World Manifest

world.join response includes manifest field:

{
  "type": "world.welcome",
  "manifest": {
    "name": "Pokemon Battle Arena",
    "description": "Turn-based Pokemon battle. Defeat opponent 3 Pokemon to win.",
    "actions": { "move": { "params": { "slot": "1-4" } }, "switch": { "params": { "slot": "1-3" } } }
  }
}