Two enhancements to the PR reviewer:
1. Monthly spend cap: tracked in Repo Variables (CTO_REVIEW_MONTH,
CTO_REVIEW_SPEND_CENTS, CTO_REVIEW_CAP_CENTS). Default cap $10/month.
Auto-resets on month rollover. Posts a skip-comment on PRs when cap hit.
2. A/B harness: reviews every PR with 3 models in parallel
(Claude Haiku 4.5, DeepSeek V3.1, Kimi K2 Thinking). Comment shows
all 3 verdicts side-by-side so we can compare quality/cost on real
PRs before picking a permanent default. Drop to 1 model by editing
the MODELS list after A/B window closes.
Agent-Session: cowork-reviewer-ab-20260414
de76f26b1a