Implement skill — test-integration-standards

[miroslavpojer]

Implements the test-integration-standards agent skill.

Skill file: skills/test-integration-standards/SKILL.md

Sections to implement:

• Test tier definition (unit / integration / e2e)
• When NOT to mock in integration tests — use real containerised infra, mock only external third-party services
• Real resources — approved patterns (Testcontainers, LocalStack, WireMock)
• Isolation and cleanup — per-test teardown, no execution order dependencies, container lifecycle
• CI behaviour — runnable without manual setup, unit/integration separation, slow test gating
• E2E specifics — critical journeys only, no shared state, reproducible failure artifacts