- Rename `evolution_tier` parameter to `refractor_tier` in compute_variant_hash()
to match the refractor naming convention established in PR #131
- Update hash input dict key accordingly (safe: function is new, no stored hashes)
- Update test docstrings referencing the old parameter name
- Remove redundant parentheses on boost_delta_json TextField declaration
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>