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).

package.json

@@ -35,7 +35,7 @@
     "launch": "node scripts/launch.mjs"
   },
   "engines": {
-    "node": ">=18"
+    "node": ">=22"
   },
   "dependencies": {
     "htm": "^3.1.1",