skill-registry-system-reminder-bloats-context-20k-per-turn

With ~170 skills registered, the full skill-registry is injected as a system reminder on every tool return, costing approximately 20k context tokens per round-trip. This makes multi-stage sessions with many tool calls impractical in a single conversation — token budget is exhausted before all stages complete. Split large multi-stage upgrades across separate sessions with explicit handoff documents.