Add test coverage checklist, report template, and stack matrix for ecommerce project

- Created a test coverage checklist to ensure comprehensive testing of backend and frontend components.
- Added a test report template to standardize reporting on test execution results and gaps.
- Introduced a test stack matrix to guide the selection of testing tools and frameworks for backend and frontend.
- Established a skill for repairing failing tests, including a failure triage checklist and a test repair template.
- Documented recommended MCP stack for ecommerce development with FastAPI and React/Next.js.
- Developed a detailed README outlining the project structure, agent capabilities, and recommended workflows.
- Compiled a comprehensive workflow guide detailing step-by-step commands for project setup, testing, and SEO implementation.

site-fullstack/.github/skills/ecommerce-store-foundation/assets/split-backend-agents-template.md

@@ -0,0 +1,20 @@
+# AGENTS.md Template For Split Backend Repo
+
+## Repo role
+- This repo owns FastAPI services, database models, auth, admin APIs, and integrations.
+- It serves the storefront and admin frontend repo through explicit contracts.
+
+## Backend scope
+- Catalog, taxonomy, auth, customers, carts, orders, content, settings, and admin operations.
+- Migrations, background jobs, storage, and integration boundaries.
+
+## Contract rules
+- Keep OpenAPI and schema naming stable.
+- Document any breaking change for the frontend repo before implementation.
+
+## Security and roles
+- Separate customer and staff permissions.
+- Apply RBAC for admin operations.
+
+## Delivery rules
+- Maintain migration safety and predictable local development.