Add a pure fleet snapshot assessor and a read-only controller/reconciler
MCP tool so multi-instance fleets can be enumerated by client_instance_id
without treating shared client_type as duplication. Trusted launcher
instance IDs, classification (missing/unmanifested/collisions/historical),
registry schema extensions, docs, and regression tests for #978.
Closes#978
Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
