Fix pre-existing master Check failures

[spozitivom]

Summary

This PR fixes the pre-existing red Check on race-sdk/master as a separate stabilization cleanup, without mixing it with guest-mode development.

The scope is intentionally narrow:

• no guest bootstrap redesign
• no workspace refactor
• no new product features
• no changes outside race-sdk

Root cause

The current master workflow path was:

npm i -ws
npm run build --prefix ./packages/borsh
npm run build --prefix ./packages/sdk-core
npm test -ws

The build steps were already green.

The failure was isolated to the Check step and only to these packages:

• @race-foundation/sdk-core
• @race-foundation/sdk-solana

The actual causes were deterministic and pre-existing:

• legacy tests in sdk-core were out of sync with current event/encryptor behavior
• sdk-solana tests were still written against older account/instruction contracts
• one sdk-solana test still imported @solana/web3.js instead of the current @solana/kit-based model
• sdk-core RSA test failures exposed a real implementation issue: RSA-OAEP with SHA-256 was using a 512-bit modulus, which is too small for the tested encryption path
• the existing sdk-core test suite still expected small backward-compatible Encryptor helpers that were no longer present

What changed

sdk-core

• increased RSA modulus size from 512 to 2048 for generateRsaKeypair()
• restored small compatibility helpers used by the existing test suite:
• Encryptor.create(...)
• encryptor.exportPublicKey()
• updated one outdated event test expectation to match the current GamePlayer shape

sdk-solana

• updated instruction tests to current constructor/serialization contracts
• updated account tests to current account shapes
• replaced outdated @solana/web3.js test usage with @solana/kit

Verification

The exact current workflow path now passes locally:

npm i -ws
npm run build --prefix ./packages/borsh
npm run build --prefix ./packages/sdk-core
npm test -ws

Additional targeted verification:

• npm test --workspace @race-foundation/sdk-core
• npm test --workspace @race-foundation/sdk-solana

Notes

This PR is intentionally separate from guest-mode work.

It does not:

• modify racepoker
• modify race-holdem
• add new guest features
• redesign SDK architecture
• attempt a broad cleanup outside the current failing Check