20260903T1810Z docs structure migration

What. The docs-structure proposal executed (D28). Concepts and invariants moved verbatim from architecture.md into docs/domain.md, plus invariant 10. docs/scenarios/ created with the format and index; the scenarios themselves land one PR each, reviewed individually (first eight: PR #3). docs/open-questions/ created, one file per open decision, seeded with the six raised in review. docs/design/conventions.md holds the skeleton proposal's nine conventions as current truth, so the frozen proposal is cited for history only. relationships.md, v0-review.md, and skeleton-proposal.md moved to docs/proposals/ and frozen. The v1 relation attribute schemas (D19) now live in interfaces.md's registry section, so the freeze orphans nothing. writing-docs skill (ten types, domain, scenario, proposal, open question, and data model rules), CLAUDE.md read order, PRD appendix, README, and the site nav updated. Every cross-reference resolves under the strict build.

Why. One place per definition, and a visible boundary between current truth and history; Benve's review round 1 (attribute schemas, D27 history link) folded in. Event vs Episode deferred by Nacho, not a priority.

Verify. make docs-build exits 0; docs/domain.md has ten invariants; ls docs/design shows only architecture.md, interfaces.md and the excalidraw file; D28 in docs/decisions.md.