Validate schema when fetching code.json

Would be nice to have a system where each code.json is validated against the actual code.json schema so that we can build out a compliant index.json without having any non-compliant code.json files in there. Would heavily reduce manual work.

Start by tracing where the tool fetches each code.json and where it builds index.json, then review the actual code.json schema used for compliance. The work is done when fetched code.json files are validated before inclusion and non-compliant files cannot enter the generated index.json.

Written by the indexing model from the issue text.