fix(ui): prevent empty space in package grid when readme is short

The 1280px+ breakpoint had no explicit grid-template-rows, so extra
sidebar height was distributed across all rows. Adding auto auto auto 1fr
pushes extra space into the readme row instead of the install/vulns area.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: howwohmm

app/pages/package/[[org]]/[name].vue

@@ -1120,6 +1120,7 @@ const showSkeleton = shallowRef(false)
       'install sidebar'
       'vulns   sidebar'
       'readme  sidebar';
+    grid-template-rows: auto auto auto 1fr;
   }
 }