fix(docs-site): add docs index redirect, test, and trim Accept media type

Redirect bare /docs to the introduction page with proper metadata
resolution. Add a test for the redirect. Trim the media type in the
Accept header parser so whitespace around semicolons does not break
markdown content negotiation. Add a test script to package.json.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs-site/middleware.ts

@@ -38,7 +38,7 @@ function isMarkdownPreferred(acceptHeader: string | null) {
         .find((parameter) => parameter.startsWith("q="));
 
       return {
-        type: type.toLowerCase(),
+        type: type.trim().toLowerCase(),
         quality: quality ? Number.parseFloat(quality.slice(2)) : 1,
         index,
       };