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-repair/assets/failure-triage-checklist.md

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+# Failure Triage Checklist
+
+## First classify the problem
+- Real product bug.
+- Broken or outdated test.
+- Environment or fixture problem.
+- Flaky timing or async issue.
+- Wrong assumptions after a refactor.
+
+## Backend-specific checks
+- Contract mismatch.
+- Validation error changes.
+- Permissions or auth regression.
+- Test data or fixture drift.
+
+## Frontend-specific checks
+- UI behavior changed intentionally or unintentionally.
+- Query selectors too brittle.
+- Async rendering not awaited correctly.
+- Mock data drift.
+
+## Repair rule
+- Fix the real source of truth issue first.
+- Only change tests when the implementation is correct and the test is outdated or wrong.