feat: scheduled consolidation with change budgets and cost tracking

[salishforge]

Summary

Add support for scheduled sleep cycles with change budget caps and LLM cost tracking per cycle.

Design

• Add optional cron-triggered sleep cycle endpoint (or document external cron setup)
• Add `max_revisions_per_cycle` config (default 5) to limit changes per sleep cycle
• Track and log token usage and estimated cost per cycle
• Add `last_sleep_cycle` and `next_recommended_sleep` to agent health metrics

Inspiration

Inspired by claude-code-toolkit (MIT) auto-dream pattern — nightly batch consolidation with max 5 changes per cycle at ~$0.09/run.

Closes #54