feat: GSoC 2025 Contributions - Core Updates & Optimizations

[SH20RAJ]

This PR consolidates my initial contributions for GSoC 2025 (Core Updates & Optimizations).

Fixes & Optimizations

• Kuhn Poker: Standardized public observation strings to match perfect recall format ('b'/'p'), resolving internal inconsistencies (Issue Cool work. Do you plan to support large games, such as Texas Hold'em? #5).
• Euchre: Generalized Trick::Play logic for better readability and performance (Issue add_subdirectory given source "abseil-cpp" which is not existing #3).
• Universal Poker: Clarified betting action counts and removed confusing TODOs (Issue Infinite loop configuring CMake #4).
• Phantom TTT: Fixed history tracking to use base class history_ (Issue Public states support #1).
• Documentation: Updated public URLs for Go/PhantomGo resources (Issue Failed to invoke nproc alias #2).

Verified with kuhn_consistency_test and euchre_test.

(Removed Crazyhouse implementation as requested, as it is tracked in a separate PR)

[lanctot]

@SH20RAJ please don't cascade the contributions across PRs.

The crazyhouse implementation is in a separate PR, please remove it from this one and rename the PR accordingly.

Thanks!

[SH20RAJ]

@lanctot I have removed the Crazyhouse implementation from this PR as requested. It now only contains the core updates and optimizations for Kuhn Poker, Euchre, Universal Poker, Phantom TTT, and Documentation.

I verified the changes and force-pushed. Please let me know if anything else needs adjustment.

[lanctot]

Hi @SH20RAJ,

The quoted issues are from more than 6 years ago. Any reason you're applying fixes based on 6 year-old issues that were closed long ago?

I think I would rather keep the files as they are now.. this would introduce some backward-incompatibilities that seem like they're worth the effort.

[SH20RAJ]

Hi @lanctot, I understand! I was initially going through some of the older closed issues to find small entry-level tasks to get familiar with the codebase and architecture as part of my preparation for GSoC 2025. I didn't realize they might introduce backward incompatibilities. I'll focus my efforts on more recent and open issues going forward. Feel free to close this PR if these changes aren't needed or if you prefer keeping the files as they are. Thanks for the guidance!