Validate ctx length in MlDsa.verify (F-4014)

MlDsa.sign/sign_with_seed reject a context longer than 255 bytes with
ValueError, but verify did not. With ctxLen now correctly declared as byte in
the cdef, an over-long ctx would surface as a low-level CFFI OverflowError
instead of the consistent ValueError callers get from the signing paths.

Reject len(ctx) > 255 with ValueError in verify, matching sign.

wolfcrypt/ciphers.py

@@ -2364,6 +2364,10 @@ if _lib.ML_DSA_ENABLED:
 
             if ctx is not None:
                 ctx_bytestype = t2b(ctx)
+                if len(ctx_bytestype) > 255:
+                    raise ValueError(
+                        f"context length {len(ctx_bytestype)} too large: must be 255 or less"
+                    )
                 ret = _lib.wc_dilithium_verify_ctx_msg(
                     sig_bytestype,
                     len(sig_bytestype),