Continues the ConfigLoader.cpp domain split. StatEntry/kKnownStats are
only used by loadModules, so they move along as a domain-local
anonymous-namespace table rather than into TomlHelpers. Pure move; no
logic change.
Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG