docs: add SARIF-to-reviewdog recipe

[EmersonBraun]

What changed

• adds a tested SARIF-to-reviewdog recipe to the README and operations guide
• keeps reviewdog responsible for diff filtering and GitHub annotations
• documents least-privilege credentials, advisory defaults, and failure policy
• refreshes machine-readable documentation
• adds regression assertions for the interoperability contract

Why

AgentsKit Code Review already emits SARIF 2.1.0, while reviewdog already consumes SARIF. This recipe shows how to compose those public interfaces directly instead of introducing an AgentsKit-specific converter or upstream reporter.

Validation

• npm run check — 17 tests passed
• npm pack --dry-run — 41 files
• git diff --check

This PR is intentionally draft. It does not include an upstream reviewdog contribution, merge, release, tag, or package publication.