Added coup

[YVin3D]

Description

Adds Coup the board game.

Motivation and Context

I like Coup.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New game (adds a new game to TextArena)
• Game enhancement (improves an existing game)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)
• Refactoring (code improvement without changing functionality)

Game-specific changes

If your PR adds or modifies a game, please specify:

Adds Coup with good documentation for the code as well as implementation. Commented code so it should be easy to follow. Please see the README.md in textarena/envs/Coup for more.

Implementation Details

• Basic Play and Prompting
• Ability for other players to block/bullshit
• Ability for other players to bullshit a blocker
• Board and state rendering
• end-to-end game works with two players
• [?] end-to-end game works with >2 players

Notes:

• I can't seem to get >2-players to work consistently. It does work... most of the time. On rare occasions it just runs on for an entire game's worth of prompts without ever hitting a breakpoint in the step() function. I think it has something to do with it maxing out on invalid moves. I gave up trying to debug I'm sorry. This code is otherwise functional, though.

Testing

Describe the tests you've done to verify your changes. For game-specific changes, describe how you've tested the game mechanics.

• reasoning models
• non-reasoning models
• exchange and keep end-to-end
• you still lose your coins if your assassination is blocked
• fake block an assassination with 2 cards remaining (double hit, insta-eliminate)
• fake block an assassination with 1 cards remaining (double hit, but shouldn't crash)
• incorrect block ([block foreign aid] when last played was a tax)
• two players end-to-end
• three players end-to-end
• four players end-to-end
• five players end-to-end
• six players end-to-end
• invalid steal target player ([steal 7])
• target player on a steal doesn't have enough coins
• invalid coup
• recovery from invalid move
• forces a coup when coins >=10

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the contribution guidelines. (required)
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes. (required for bug fixes or new features)
• All new and existing tests passed.
• For game changes, I have verified that the game still runs correctly end-to-end.