Use bundled version of spectral (#35573)

To reduce the risk of npm supply chain attacks and to speed up
dependency installation, I've
[bundled](https://github.com/silverwind/spectral-cli-bundle) the
spectral package into a zero-dependency module. The upstream package is
pretty dead currently, so I expect to keep up with their updates.

The package
[exports](https://github.com/silverwind/spectral-cli-bundle/blob/de05948c53a0a6f9690cdf65d35c3fc3324a583c/package.json#L9)
a `spectral` bin script, so `pnpm exec spectral` continues to work
as-is.

In total, this removes 86 dependencies from the npm dependency tree.

package.json

@@ -67,7 +67,6 @@
   "devDependencies": {
     "@eslint-community/eslint-plugin-eslint-comments": "4.5.0",
     "@playwright/test": "1.55.1",
-    "@stoplight/spectral-cli": "6.15.0",
     "@stylistic/eslint-plugin": "5.4.0",
     "@stylistic/stylelint-plugin": "4.0.0",
     "@types/codemirror": "5.60.16",
@@ -102,6 +101,7 @@
     "material-icon-theme": "5.27.0",
     "nolyfill": "1.0.44",
     "postcss-html": "1.8.0",
+    "spectral-cli-bundle": "1.0.3",
     "stylelint": "16.24.0",
     "stylelint-config-recommended": "17.0.0",
     "stylelint-declaration-block-no-ignored-properties": "2.8.0",