scheduler_cron imported SessionId without using it; clippy unused-imports
failed the task 07 gate. tiers.rs had the same for DataClass.
Co-Authored-By: Grok 4.6 <noreply@x.ai>
Eight closed tasks for epochs and compaction, then ten for the scheduler,
ToolSummary, and tiers. Given tests first. Gate 1456 → 1507 → 1572.
Co-Authored-By: Grok 4.6 <noreply@x.ai>