Fix RSA decryption of binary data

[zhangli091011]

Description
Treat RSA ciphertext and plaintext as raw bytes instead of UTF-8 strings. This prevents binary ciphertext from being corrupted before decryption and allows non-UTF-8 plaintext, such as decrypted symmetric keys, to flow into operations like To Hex.

Existing Issue
Closes #2436.

Screenshots
Not applicable; this is an operation data handling fix.

AI disclosure
OpenCode (gpt-5.6-sol) was used to investigate the issue, implement the fix, and add the regression test. I reviewed the diff and ran the full non-UI test suite.

Test Coverage
Added an RSA-OAEP/SHA-256 regression vector covering From Hex -> RSA Decrypt -> To Hex.

• npm test: 262 Node API tests passed; 2242 operation tests passed
• npx eslint src/core/operations/RSADecrypt.mjs tests/operations/tests/RSA.mjs

[zhangli091011]

The CLA is complete, but the required main check has not been produced because the fork Pull Requests workflow is awaiting maintainer approval: https://github.com/gchq/CyberChef/actions/runs/29688294131. Could a maintainer please approve the run when convenient?

[sylvesterkaczmarek]

This looks correct and appropriately scoped. Moving RSA Decrypt to byteArray input/output removes the implicit UTF-8 decode that corrupted arbitrary binary plaintext, while the forge raw encode/decode preserves the exact encrypted/decrypted bytes. The added OAEP-SHA256 regression case exercises genuinely non-text binary output, and the existing round-trip coverage should protect the normal text path. Looks good to me.

[zhangli091011]

Friendly bump: the branch is mergeable and the only missing requirement is the fork workflow approval for the required \main\ check. Could a maintainer approve the run and review when convenient?