Unreferenced, and negatives do not exist at CFG=1 where most generation happens.
Drops _v2_negative_prompt_advisor and its two private helpers (131 lines);
_v2_negative_text_conflicts_with_request keeps 2 live callers and stays.
Tests: 968 passed, same as baseline.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>