Introduce `docs/models/` with the catalog index and its first card
(product-catalog), recording invariants, dimensions, and drift traps
per the Decision 141 documentation division. Add the model-cards
openspec change (proposal, design, spec, tasks) and sync the design
docs to v15: product kind taxonomy dissolved (Decisions 134–139),
Decisions 140–141 ratified, and product/pricing helpers updated. The
catalog is the single descriptive home for as-built models.
- Remove per-module projection files (README, architecture, companion,
interfaces, model) under design/<module>/
- Add design/documents/ with numbered design docs, references, policies,
and manifest
- Update design/README.md to describe the directory as a mirror of
membcons-db's normative surfaces
- Record Decisions 140-141 in companion and glossary; update
data-model.md schema organization
cgalo5758