Add schema-envoy to tools

[tamerkalla]

Adds schema-envoy under tools.

Every LLM provider accepts a subset of JSON Schema, so client libraries delete the keywords the provider does not list. That deletion widens the accepted value set (the converted schema accepts instances the source schema rejects), and it is normally not reported. schema-envoy performs the conversion, reports every keyword it removed, and compiles a residual validator over precisely those dropped constraints, so a caller can reject a widened value rather than only learn that widening occurred.

It is distinct from Schema Gateway, already listed: that entry compiles a schema into provider-ready request payloads and lints portability. schema-envoy's output is the report and the residual validator over what conversion cost, rather than the request payload.

Zero-config for the built-in provider targets, dual ESM/CJS, published with npm provenance.

I have added the entry to data.yaml and regenerated README.md with npm install && npm start, as CONTRIBUTING.md asks.

[cla-assistant]

All committers have signed the CLA.

[tamerkalla]

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Signed

[jviotti]

Awesome!