Objective:
Update learn/guides/devindex/frontend/ContentEngine.md to use DevIndex-specific examples instead of inheriting examples from the main Portal app.

Tasks:

• Update the tree.json snippet to reflect the structure of learn/guides/devindex/tree.json.
• Update URL hashes and file path mappings in the text to use DevIndex paths (e.g. frontend/Architecture.md).
• Update Mermaid diagram to use a DevIndex-specific URL hash.