Rewrite the host-model design note for the current architecture (entities, tables,
commands, nested validation, known limits), refresh the plan's current-state header,
the ledger and gaps-doc status lines (cadcodec PR #48), the README status and the
superseded ocs.command notes, and drop dangling references to a sibling project that
is not in this repository.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>