Add example caller workflow for workflow templates

[ktacero]

Pre-requisito

• Leer la wiki del proyecto para entender el contexto completo

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Problem

Workflow templates use workflow_call but there is no example of how repos should call them.

Action Items

• Add docs explaining how to create .github/workflows/ci.yml that calls the reusable workflows
• Include example YAML snippet in CONTRIBUTING.md or as a separate doc