fix(web): make directory browser listing scrollable

Cap inner list height at 50vh with overflow-y-auto so tall listings
don't push the projects add form off-screen on small viewports.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Seluj78

web/src/components/DirectoryBrowser.tsx

@@ -136,7 +136,7 @@ export function DirectoryBrowser({ initialPath, onSelect }: Props) {
       </div>
 
       {/* Directory listing */}
-      <div className="border border-surface-700 rounded-lg overflow-hidden" role="listbox" aria-label="Directories">
+      <div className="border border-surface-700 rounded-lg overflow-y-auto max-h-[50vh]" role="listbox" aria-label="Directories">
         {loading ? (
           // Skeleton loading rows
           <div className="animate-pulse">