feat: Add anti-sycophancy and objective metrics to EVAL mode

- Add anti-sycophancy rules prohibiting praise phrases
- Add objective metrics framework for measurable evaluations
- Restructure output to critique-first format
- Add Devil's Advocate and Impact Radius Analysis sections
- Require minimum 3 improvements per evaluation
- Update code-reviewer.json and core.md

close #70

Author: wishket-pjw