Fix 5 (Session 2B-i): system_status's own dedicated body -- always in the canonical registry (visibility="primary", category="start"), always callable free of archive/LLM credit (see _FREE_TOOLS below -- system_status is unconditionally in it), never rate-limited beyond the same abuse protection every endpoint gets.

Deliberately does NOT include database_status/project_store_status -- those describe the persistence layer this pass explicitly excludes (it needs a supervised migration). Adding placeholder fields for a layer that doesn't exist yet would be worse than omitting them.