Upgrade JSON Schema CLI to v16.2.0

[jviotti]

Signed-off-by: Juan Cruz Viotti jv@jviotti.com

[augmentcode]

🤖 Augment PR Summary

Summary: Bumps @sourcemeta/jsonschema to v16.2.0 and updates the repo’s JSON Schema CLI workflow to match.
Changes:

• Remove the obsolete meta/schemas-root.json meta-schema and the Makefile validation step that used it.
• Add a new lint rule (rules/root.json) and register it as a topLevel rule in jsonschema.json to enforce required root keywords.
• Update Makefile fmt/metaschema/lint invocations to drop the removed meta paths.

Notes: Root-keyword enforcement now happens through linting (document-root only) rather than a separate validate pass.

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[augmentcode]

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