chore: upgrade to NPM v12

.github/actions/install-npm/action.yml

@@ -0,0 +1,14 @@
+name: Install NPM
+description: >
+  Installs the NPM version required by the `engines.npm` directive in
+  package.json, which is required for the project to build correctly.
+
+runs:
+  using: composite
+  steps:
+    - name: Install NPM
+      shell: bash
+      run: |
+        npmVersion="$(node -p 'require(`${process.env.GITHUB_WORKSPACE}/package.json`).engines.npm')"
+        echo "Installing npm@${npmVersion}"
+        npm install -g "npm@${npmVersion}"

.github/workflows/test-and-release.yaml

@@ -22,6 +22,9 @@ jobs:
           node-version: ">=24.18.1 <25"
           cache: "npm"
 
+      - name: Install NPM version specified in package.json
+        uses: ./.github/actions/install-npm
+
       - name: Install dependencies
         run: npm ci --no-audit
 

README.md

@@ -23,3 +23,13 @@ const fetch = fetchWithDebug(
 
 const res = await fetch(new URL("https://example.com"));
 ```
+
+## Node & NPM
+
+This project requires npm `>=12.0.2 <13` (enforced via `check-node-version` on
+`npm install` and `npm ci`).
+
+The check is skipped during `npm publish` and `npm pack`, because
+`semantic-release` bundles its own npm (`@semantic-release/npm` depends on
+`npm@^11.6.2`) and runs the publish with that version rather than the one
+installed in CI.

package.json

@@ -12,13 +12,15 @@
   },
   "author": "Nordic Semiconductor ASA | nordicsemi.no",
   "scripts": {
-    "test": "node --no-warnings --experimental-transform-types --test \"./*.spec.ts\""
+    "test": "node --no-warnings --experimental-transform-types --test \"./*.spec.ts\"",
+    "prepare": "case \"$npm_command\" in install|ci) check-node-version --package ;; esac"
   },
   "license": "BSD-3-Clause",
   "type": "module",
   "main": "export.ts",
   "devDependencies": {
     "@bifravst/prettier-config": "1.1.17",
+    "check-node-version": "4.2.1",
     "nock": "14.0.17",
     "prettier": "3.9.6"
   },
@@ -33,5 +35,8 @@
       "@semantic-release/release-notes-generator",
       "@sebbo2002/semantic-release-jsr"
     ]
+  },
+  "engines": {
+    "npm": ">=12.0.2 <13"
   }
 }