fix(ui): cap workspace browser at 36% max width

The empty-state workspace shell (used on index and search pages) was
using a 50/50 grid split. When the miller-browser only shows 1-2 columns
the left side looks too wide. Change to a 36/64 split so the browser
column maxes out at 36% while keeping its 300px minimum.

apps/server/internal/httpserver/static/site.css

@@ -552,9 +552,9 @@ code {
   grid-template-columns: minmax(260px, 0.38fr) minmax(0, 1fr);
 }
 
-/* Empty state: more balanced 50/50 feel */
+/* Empty state: browser capped at 36% max */
 .workspace-shell--empty {
-  grid-template-columns: minmax(300px, 1fr) minmax(300px, 1fr);
+  grid-template-columns: minmax(300px, 0.5625fr) minmax(300px, 1fr);
 }
 
 /* Miller browser - flex layout so all columns are visible as vertical slices */