Two new short docs unblock new contributors who currently have to read
the Go source to figure out the GITHUB_TOKEN requirement and the
agents.yml schema:
- docs/LOCAL_DEV.md walks through the PAT setup, the local run command,
what files the run modifies, and how to revert before opening a PR.
- docs/CONTRIBUTING.md documents the agents.yml fields, enumerates the
six valid category values, and explains the rename and deprecation
policy now that history is keyed canonically.
Also add a one-sentence caption under the table in readme.tmpl so the
Delta7d column has a definition in the rendered README.
