ci: fix broken vnu download and linkedin link-check 404

[savvides]

Summary

Both CI jobs ("Validate HTML" and "Check Links") have been red on main since at least the v2.1.0 docs sync (2026-04-25). Two unrelated infra issues, both fixed here in one workflow file.

Validate HTML

Was downloading vnu from:

https://github.com/validator/validator/releases/latest/download/vnu.jar_dist.zip

The validator project doesn't publish GitHub Releases (only tags), so the URL 404s and unzip exits 9 before vnu ever runs. Confirmed via gh api repos/validator/validator/releases returning [].

Replaced with the official vnu-jar npm package (v26.4.16, published 2026-04-16 by the same project). It bundles vnu.jar and exposes it at a stable path: node_modules/vnu-jar/build/dist/vnu.jar. Verified locally that npm install --no-save vnu-jar lands the jar at exactly that path. Also dropped the apt install of default-jre because ubuntu-latest runners ship with Java preinstalled.

Check Links

The lychee link checker hits https://www.linkedin.com/in/savvides/ (legitimate footer link added in 7df0451) and gets a 404 because LinkedIn returns 404 for unauthenticated profile requests from non-browser user agents. Added --exclude linkedin.com to the lychee args.

Diff

-      - name: Install vnu
-        run: |
-          sudo apt-get update -qq
-          sudo apt-get install -y -qq default-jre
-          curl -sL https://github.com/validator/validator/releases/latest/download/vnu.jar_dist.zip -o vnu.zip
-          unzip -q vnu.zip
+      - name: Install vnu-jar
+        run: npm install --no-save vnu-jar

       - name: Validate HTML
-        run: java -jar dist/vnu.jar --errors-only index.html
+        run: java -jar node_modules/vnu-jar/build/dist/vnu.jar --errors-only index.html
...
-          args: --exclude fonts.googleapis.com --exclude fonts.gstatic.com --exclude d3js.org --exclude localhost ...
+          args: --exclude fonts.googleapis.com --exclude fonts.gstatic.com --exclude d3js.org --exclude linkedin.com --exclude localhost ...

Test plan

• CI runs on this PR. Both jobs should now go green.
• After merge, confirm the next push to main shows green CI for the first time since v2.1.0.

🤖 Generated with Claude Code

[gemini-code-assist]

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