Add Ants arena (fog-of-war swarm RTS)

[john-b-yang]

Summary

Adds Ants, a fog-of-war swarm RTS in the spirit of the 2010 Google/Waterloo Ants AI Challenge. Each player commands many ants on a toroidal grid; every turn all ants move one cell at once. Highlights:

• Fog of war — you only see within your ants' view radius; you remember the rest yourself.
• Focus-fire combat — an ant dies unless it has strictly fewer attackers than every enemy attacking it (locally outnumbered = dead), so ganging up wins fights.
• Food → growth — food adjacent to a single player's ants spawns a new ant on a hill.
• Hills & razing — move onto an enemy hill to raze it; most hills razed (tiebreak: ants alive) wins.

Engine lives in its own repo (cloned by the Dockerfile, matching the other arenas): CodeClash-ai/Ants.

Bot API

def do_turn(obs: dict) -> list:   # list of [row, col, "N"/"S"/"E"/"W"] moves

Fog-limited obs: turn/max_turns, rows/cols (toroidal), the *radius2 constants, my_ants, my_hills, and only-where-visible enemy_ants, enemy_hills, food, water. do_turn runs in one long-lived process, so bots can remember the discovered map in module globals. Un-ordered ants stay; moving into water is ignored; two ants onto one cell both die.

Features

• Deterministic + replayable, seeded per sim (symmetric maps/water/food vary per seed; half-shift symmetry makes 2-player games fair).
• N-player capable (2-player default).
• Replay renderer — spectator view of ants/hills/food/water with per-player ant & hill counts, per-sim winner via peek_winner.
• Swarm starter bot (remembers water/hills, seeks food, razes known enemy hills, explores, avoids self-collisions) + README documenting the API and turn resolution.

Testing

• Deterministic (same seed → identical games); starter beats an idle bot 10–0; ants grow, combat + razing occur; 3/4-player free-for-alls work.
• Fog verified (enemy hill at dist²=512 invisible under view²=77; partial water visibility); maps verified symmetric + connected.
• Full codeclash run configs/test/ants.yaml end-to-end (Docker build, sims, scoring, replay) passes.