gh-ocannl-57: complete decoder-only transformer example on Names dataset Use library decoder_only_block in layer_norm_test (replacing local mini_decoder_block duplicate), update README checklist and CHANGES.md. The core implementation (decoder_only_block/decoder_only in nn_blocks.ml, transformer_names.ml training + generation, dune stanza, expected output) was added in prior commits on this branch. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>