Add repo scaffolding to meet repository standards

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.

Dockerfile

@@ -0,0 +1,11 @@
+# node 22-alpine, 2026-02-22
+FROM node@sha256:e4bf2a82ad0a4037d28035ae71529873c069b13eb0455466ae0bc13363826e34
+
+RUN apk add --no-cache make
+
+WORKDIR /app
+COPY package.json yarn.lock ./
+RUN yarn install --frozen-lockfile
+COPY . .
+
+RUN make check