fix(ci): install site deps in release preflight (#7)

Release preflight runs check:site, which invokes site:build (Eleventy). Root npm ci does not install site/package.json dependencies, so Eleventy was missing and preflight failed with exit 127.\n\nInstall site dependencies in preflight before check:site so release validation matches the expected environment and can proceed to npm publish.

Author: stevenobiajulu

.github/workflows/release.yml

@@ -86,6 +86,9 @@ jobs:
       - name: Regenerate and verify tool reference docs are committed
         run: npm run check:tool-docs
 
+      - name: Install site dependencies
+        run: npm --prefix site ci
+
       - name: Build site and validate internal links
         run: npm run check:site