Node 22+ everywhere, LF text on Windows checkouts, CI actions v7

- Node minimum is 22 in package.json engines, the start scripts, the service installer, setup and doctor,
  matching the README, the release notes and the CI matrix (22 / 24).
- .gitattributes: CSS, HTML, JSON, Markdown and YAML check out with LF, so `node --test` on Windows matches the
  CSS rules the UI tests read; the Windows test step is no longer continue-on-error.
- CI: actions/checkout@v7 and actions/setup-node@v7 (Node 24 runtime).

.github/workflows/ci.yml

@@ -31,9 +31,9 @@ jobs:
       RENDER_E2E: '0'
       NO_COLOR: '1'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v7
         with:
           node-version: ${{ matrix.node }}
           cache: npm
@@ -46,8 +46,6 @@ jobs:
 
       - name: Unit & integration tests
         run: node --test
-        # Linux is the reference platform; Windows results are informative until the suite is proven there.
-        continue-on-error: ${{ matrix.os == 'windows-latest' }}
 
       - name: Server smoke test (boot, /healthz, index.html, doctor)
         shell: bash