revert entity extraction to segment schedule
Cross-workstream review identified that facets agent (priority 90)
reads {segment}/agents/entities.md as input. Moving entities to
activity schedule would break facet classification. Entity redundancy
is instead handled by the change-detection gate which skips all
priority-10 agents during idle/low-change segments.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>