Migrate Nonlocal Games katas to quantum.microsoft.com

Nobody has claimed this yet.

Current [CHSH game](https://github.com/microsoft/QuantumKatas/blob/main/CHSHGame), [GHZ game](https://github.com/microsoft/QuantumKatas/blob/main/GHZGame), and [Mermin-Peres magic square game](https://github.com/microsoft/QuantumKatas/blob/main/MagicSquareGame) katas cannot be used with the modern QDK. It would be nice to have them available as part of the [new katas experience](https://quantum.microsoft.com/en-us/experience/quantum-katas).

I think each of them is too small to warrant a separate kata in the new experience, so it would make sense to merge them together into one kata called "Nonlocal Games: CHSH, GHZ, and Mermin-Peres".

We'll probably want to explain each quantum strategy ahead of the exercises that implement it, same as we did in QEC Shor kata, since it's tricky to come up with independently (especially for the magic square!)

* [x] CHSH game: Keep task 1.1, merge two cells in task 1.2 in one task by defining an operation that returns a tuple of two operations, one for Alice and one for Bob, drop 2.1 and 2.3, keep 2.2 and 2.4-2.5 (possibly make 2.5 a demo), keep the discussion of quantum strategy and its win probability.
* [ ] GHZ game: Keep task 1.1, merge 1.2 and 1.3 in a more open-ended task that evaluates success probability of a classical strategy, keep 1.4 and 2.1-2.3 (possibly make 2.3 a demo), keep the discussion of quantum strategy and its win probability.
* [ ] Mermin-Peres: Merge 1.1.1 and 1.1.2 into one task with Boolean flag `isAlice`, keep 1.2 and 1.3 (merge two cells in 1.3 in one task returning a tuple), keep 2.1, drop 2.2 (it will be verified in 2.3 automatically), keep 2.3-2.7.

Start with the existing CHSHGame, GHZGame, and MagicSquareGame katas and compare their structure with the new katas experience and the QEC Shor kata. Implement the combined “Nonlocal Games: CHSH, GHZ, and Mermin-Peres” kata using the listed task merges, removals, strategy explanations, and win-probability exercises; done means all three games are available in the modern QDK experience.

Written by the indexing model from the issue text.