Add mixed-parameter HSS support - #56

Move the HSS signer and verifier off the uniform LMS/LM-OTS traits and onto the per-level HSS_Params accessors.

HSS_Params is still uniform, so every level resolves to the same LMS/OTS pair and signing and verification behaviour is unchanged.

Move HSS_Params to the HSSLevel parameter-pack shape and migrate the shipped uniform typedefs to repeated level descriptors.

Runtime behaviour is unchanged; mixed-level dispatch remains gated for the next step.

Build per-call level tables for HSS signing and verification, and use per-level params and sizes when decomposing indexes, building subtree chains, emitting signatures, and verifying each layer.

Remove the mixed-parameter gate. Add a height-mixed L=2 test covering sign/verify, tamper rejection, and restart across a bottom-subtree rollover.

Adds the remaining SHA-256/N32 LM-OTS parameter sets, explicit LMS H5/H10 instantiations, and H5 sign/verify coverage for each new set.

Add HSS_SHA256_H10W4_H5W8_L2, a two-level HSS set with an H10/W4 root over an H5/W8 leaf, and instantiate the HSS class templates for it.

Add a verify-only RFC 8554 Appendix F Test Case 2 known-answer test. TC2 mixes parameters across levels, giving coverage for W4 and mixed-level verification.

Lock TotalSignatures(), PublicKeySize(), and SignatureSize() for the uniform HSS typedefs with compile-time assertions.

Add deterministic L=2 golden signature checks using fixed SEED, I, and a fixed 0xC5 signing RNG; the goldens are regression fixtures captured from this implementation. Cover L=3 and L=4 with deterministic sign/verify round-trips and SignatureSize() checks, keeping full byte fixtures to L=2 to limit test data.

TC2 verifies the H10/W4 over H5/W8 typedef against the RFC vector, but only on the verify side. Add the existing generic HSS signing tests for that typedef so the mixed-W signing path is covered too.

The private H10/H5 test parameter set was explicitly instantiated in lms.cpp, which would export its symbols from the Unix shared library. The public H10/W4 over H5/W8 typedef exercises the same mixed-height dispatch and adds mixed W, so the boundary, tamper and restart coverage runs on it instead and the private instantiations are removed.

A mismatched parameter pair would feed an N-byte LM-OTS result into buffers sized from LMS M. Add a CompatibleLMSParams trait, assert it in every LMS template that composes the pair, and route the per-level HSS check through it. All shipped parameter sets are 32/32, so this rejects inconsistent descriptors at compile time without changing any current configuration.

Index the bottom level explicitly in the uniform boundary tests, and restore the safety-boundary wording on the HSS signer reservation comment.