`package.json` now carries `"license": "MIT"`, matching `LICENSE`. Without it yarn printed `warning package.json: No license field` and `warning No license field` each time `script/bootstrap` ran inside the Docker phases of `make check`. No other yarn warning appears in the bootstrap output.
Model: opus-5-5
Add .gitignore, LICENSE (MIT), Makefile, Dockerfile, .dockerignore,
and pin prettier via yarn lockfile for integrity-checked markdown
formatting. Update REPO_POLICIES.md self-reference to point to this
repo. Format markdown files with prettier.