fix(docs): pin Node heap to 8 GB for the VitePress production build

The 44-project docfx expansion generates ~2145 pages and the VitePress
production build exceeds Node's default 4.2 GB heap, exiting 134 on
ubuntu-latest. The Docs site workflow sets NODE_OPTIONS at the job
level; the build-test-coverage workflow does not — so the
RouteCheckTests OneTimeSetUp invocation of npm run build OOM-aborted
there.

Bake the heap setting into the npm script itself by invoking
node --max-old-space-size=8192 against the vitepress bin. This avoids
shell-prefix env syntax that would break on Windows, avoids adding
cross-env as a dependency, and ensures every caller — workflow, test
fixture, manual invocation — inherits the heap setting.

Author: ottobolyos

docs/package.json

@@ -9,7 +9,7 @@
     "predev": "npm run regen",
     "dev": "vitepress dev",
     "prebuild": "npm run regen",
-    "build": "vitepress build",
+    "build": "node --max-old-space-size=8192 node_modules/vitepress/bin/vitepress.js build",
     "preview": "vitepress preview",
     "check-links": "node scripts/check-broken-links.mjs ."
   },