fix(markdown): disable directive parsing and add regression coverage

www/package.json

@@ -18,6 +18,7 @@
     "audit:blog": "node tools/audit-blog-content.mjs",
     "audit:routes": "node tools/audit-routes.mjs",
     "test:routes": "node --test tools/audit-routes.test.mjs",
+    "test:markdown": "node --test tools/markdown.test.mjs",
     "generate:sitemap": "node tools/generate-sitemap.mjs",
     "generate:redirects": "node tools/generate-redirects.mjs"
   },