bias-assessor

Use when `evidence-review` has an extraction table and needs lightweight risk-of-bias fields. **Trigger**: bias, risk-of-bias, RoB, evidence quality, 偏倚评估, 证据质量. **Use when**: `evidence-review` 已生成 `papers/extraction_table.csv`，需要在 synthesis 前补齐偏倚/质量字段。 **Skip if**: 不是 evidence/systematic review，或还没