docs: add guide for optional output-format dependencies and strict JSON consumer validation

[bogusdeck]

Summary

This PR addresses two documentation issues:

1. docs: add a focused guide for optional output-format dependencies #346: Add a guide for optional output-format dependencies.
2. docs: document strict JSON consumer validation with Node #345: Document strict JSON consumer validation with Node.js.

Changes

• docs/output-contracts.md

  • Added a table documenting optional output-format dependencies, including yaml and rich.

• docs/json-contracts.md

  • Added a section explaining how to validate base CLI JSON and NDJSON output using Node.js's JSON.parse.

Notes

Both changes are documentation-only and follow the acceptance criteria defined in their respective issues.