Type Model Target mock JSON

[adamtheturtle]

Summary

• define and document a recursive JSON value type with the public Model Target types
• use it for persisted dataset requests, generation warnings, status response bodies, and Model Target Web API validation
• remove seven Pyrefly suppressions without replacing them with broader ignores

Validation

• uv run --group=dev prek run --all-files --hook-stage pre-commit
• uv run --group=dev prek run --all-files --hook-stage pre-push
• documentation and spelling builds
• focused public Model Target and Flask integration paths (573 passed, 244 live-service cases skipped)

The complete local suite also includes live Vuforia cases and requires external credentials; CI covers that matrix.