Add warning on search for user-key linkage unreliability

frontend/src/components/SearchView.tsx

@@ -243,6 +243,11 @@ export function SearchView({
               Tip: use <code>user:</code> or <code>channel:</code> for keys or names, and wrap names
               with spaces in them in quotes.
             </p>
+            <p className="mt-2 text-xs">
+              Warning: User-key linkage for group messages is best-effort and based on correlation
+              at advertise time. It does not account for multiple users with the same name, and
+              should be considered unreliable.
+            </p>
           </div>
         )}
 

frontend/src/test/searchView.test.tsx

@@ -71,6 +71,9 @@ describe('SearchView', () => {
     render(<SearchView {...defaultProps} />);
     expect(screen.getByText('Type to search across all messages')).toBeInTheDocument();
     expect(screen.getByText(/Tip: use/i)).toBeInTheDocument();
+    expect(
+      screen.getByText(/User-key linkage for group messages is best-effort/i)
+    ).toBeInTheDocument();
   });
 
   it('focuses input on mount', () => {