chore: remove session review reports before PR

docs/reviews/ holds session-scoped multi-agent review working notes, not
shippable artifacts (CLAUDE.md Section 5).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012X9qhQT4NwmCHjdndwNtFD

Author: claude