fix: use pathname:// for package browser footer link

The footer's Package browser link pointed at /packages/ as a plain
internal href, so Docusaurus's broken-link checker flagged it on every
page since /packages is a static-only asset with no matching route,
even though the file exists under static/packages/ and the link works.
download.mdx already used the pathname:// escape hatch for the same
target; apply it here too.

Assisted-by: Claude Code:claude-sonnet-5

Author: gsanchietti

docusaurus.config.ts

@@ -147,7 +147,7 @@ const config: Config = {
           items: [
             {
               label: 'Package browser',
-              href: '/packages/',
+              href: 'pathname:///packages/',
             },
             {
               label: 'GitHub',