Review agent PRs with three small CLIs (no LLM)

Three new Go CLIs (gitdigest, ownerdiff, lockglance) help review agent PRs by answering key questions about where work landed, who owns files, and what dependencies moved. These tools provide human-readable output and can be used locally without network access. To use them, install the review-kit with a one-shot installer and then use the tools to analyze your codebase. The tools can be used in a CI workflow to provide sticky comments on PRs.