SHA3-08 TupleHash and TupleHashXOF

[turkananation]

SHA3-08 TupleHash and TupleHashXOF

Summary

Implement TupleHash128, TupleHash256, TupleHashXOF128, and TupleHashXOF256.

Scope

• Encode every tuple element with encode_string.
• Preserve empty tuple elements.
• Add NIST TupleHash and TupleHashXOF examples.
• Add tuple-boundary ambiguity tests.

Acceptance criteria

• NIST TupleHash vectors pass.
• [ab, c] differs from [a, bc].
• [a, empty, b] differs from [a, b].
• Fixed-output and XOF mode are separated.

References

• doc/FIPS202_SP800185_RELEASE_GUIDE.md - TupleHash and TupleHashXOF
• SP 800-185 Section 5

Priority: P1