Rename kind to input_kind at key 2 (the wire is the slot key; no golden byte moves).
nil_positions.rs walks every array element of every value golden, splices nil over it and
records whether the Rust decode door accepts it, into goldens/nil-positions.tsv. The tsv is
blessed by the next commit; this one builds, and its nil test fails until then.
golden_bytes, blessing and goldens_dir move to tests/common so both test files share one path.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
9ed4a72a53