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-test-implementation/assets/test-stack-matrix.md

@@ -0,0 +1,20 @@
+# Test Stack Matrix
+
+## Backend
+- Prefer the existing Python test runner and fixtures setup.
+- If the project is FastAPI and already uses `pytest`, extend `pytest` rather than introducing another runner.
+- Respect async testing patterns already present in the project.
+
+## Frontend
+- Prefer the existing frontend test stack from `package.json`.
+- Typical unit and integration options: Vitest or Jest with Testing Library.
+- Typical UI or end-to-end options: Playwright when the project already uses it or clearly benefits from it.
+
+## If the project has no test stack
+- Backend default: `pytest`.
+- Frontend default for React and Next.js component testing: Vitest plus Testing Library when compatible with the project.
+- End-to-end tests should be added only if they materially improve coverage and the project can support them.
+
+## Execution principle
+- Run only the relevant suites for the change set when that is enough.
+- If the task is broad, run both backend and frontend suites or document what was not run.