fix(ui): hide assignee name in search results on mobile

On small screens, the assignee Identity badge takes up valuable space
in the command palette search results, truncating issue titles. Hide
it below the `sm` breakpoint so more of the title is visible.

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

ui/src/components/CommandPalette.tsx

@@ -187,7 +187,7 @@ export function CommandPalette() {
                   <span className="flex-1 truncate">{issue.title}</span>
                   {issue.assigneeAgentId && (() => {
                     const name = agentName(issue.assigneeAgentId);
-                    return name ? <Identity name={name} size="sm" className="ml-2" /> : null;
+                    return name ? <Identity name={name} size="sm" className="ml-2 hidden sm:inline-flex" /> : null;
                   })()}
                 </CommandItem>
               ))}