JSON Output + V1 Endpoints

V1 introduces JSON output alongside CSV. Every V1 report accepts an output field set to json or csv, so a report can be consumed programmatically without parsing a CSV first. The response shape is documented per endpoint, with worked examples.

V1 also standardizes date filtering across reports and adds optional detail columns to the Coach report through include_skills and include_use_cases. The V0 CSV endpoints remain available and unchanged for existing integrations.