Update dependencies and move from yarn to npm

Notably, we can remove jest in favor of Node.js's built-in test runner.

Author: domenic

.github/workflows/build.yml

@@ -20,6 +20,6 @@ jobs:
     - uses: actions/setup-node@v4
       with:
         node-version: ${{ matrix.node-version }}
-    - run: yarn --frozen-lockfile
-    - run: yarn lint
-    - run: yarn test
+    - run: npm ci
+    - run: npm run lint
+    - run: npm test