CI: typecheck, lint and the vitest suite on Node 22 with a frozen pnpm lockfile (Track Q — Games was the last service without CI)

ddiff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
nnew file mode 100644
iindex 0000000..afced98
---- /dev/null
++++ b/.github/workflows/ci.yml
@@@ -0,0 +1,19 @@
++name: ci
++on:
++  push:
++    branches: [main]
++  pull_request:
++jobs:
++  test:
++    runs-on: ubuntu-latest
++    steps:
++      - uses: actions/checkout@v4
++      - uses: pnpm/action-setup@v4   # version from package.json "packageManager"
++      - uses: actions/setup-node@v4
++        with:
++          node-version: 22.22.1   # production runs Node 22 (better-sqlite3 is native: build it for this ABI)
++          cache: pnpm
++      - run: pnpm install --frozen-lockfile
++      - run: pnpm typecheck
++      - run: pnpm lint
++      - run: pnpm test