ML-DSA: missing context encoding step (only internal functions implemented?)

[larabr]

It seems that the exposed mldsa sign and verify functions correspond to ML-DSA.Sign_internal and Verify_internal (i.e. Algo 7 and 8 in FIPS 204), rather than Algo 2 and 3, which additionally encode a context string in input.

Is this intended? If so, I think this should be clarified in the README, as interoperability with other libs is affected.

[paulmillr]

f3580af will expose context-based methods.

However, there are no test vectors for that.

Branch wycheproof incorporates vectors from C2SP/wycheproof#112, but the upstream PR is not merged yet and unclear when it will be.