feat(F-001): scaffold modular monolith skeleton with boundary checker

- TypeScript + Fastify skeleton under project/ (src/modules, shared, infrastructure, app)
- scripts/check-module-boundaries.mjs enforcing module public-API rules (tested with fixtures)
- GET /health endpoint, error envelope without stack leakage
- specs/F-001-scaffold (SPEC/DESIGN/TASKS/TESTS), spec/tech.md dependency justification
- 30-ticket MercadoDeVida roadmap in backlog/features.json, spec/roadmap.md
- All gates approved: reviewer, security, qa; verify.sh green

CHECKPOINTS.md

@@ -0,0 +1,21 @@
+# CHECKPOINTS
+
+## C1 — Estructura
+- [ ] Existe `harness/`, `spec/`, `backlog/`, `work/`, `scripts/`, `platforms/`.
+
+## C2 — Estado
+- [ ] Máximo una feature en `in_progress`.
+- [ ] Estados válidos en backlog.
+
+## C3 — Gates
+- [ ] Toda feature `done` tiene `reviewer.json` aprobado.
+- [ ] Toda feature `done` tiene `security.json` aprobado.
+- [ ] Toda feature `done` tiene `qa.json` aprobado.
+- [ ] Toda feature `done` tiene `leader-close.json` válido.
+
+## C4 — Verificación
+- [ ] `./scripts/verify.sh` termina en OK.
+
+## C5 — Trazabilidad
+- [ ] `work/history.md` actualizado en cierre.
+- [ ] Artefactos por feature en `work/artifacts/<feature_id>/`.