fix: show placeholder when public feedback text is empty

Early submissions (before today's fix) have no public feedback text.
Show 'No public feedback shared yet.' instead of empty curly quotes.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 02919104-34f1-44e8-91db-7bfd688b1b6e

Author: Devyani Jain

index.html

@@ -686,7 +686,9 @@ <h3 class="h3">This art inspiration</h3>
       chip.style.backgroundColor = REL_CHIP_DULL[color] || 'var(--fg-blue-dull)';
       chip.style.borderColor     = DOT_BORDER_COLOR[color] || '#00CCCF';
 
-      document.getElementById('vw-feedback').textContent = '\u201c' + f.t + '\u201d';
+      document.getElementById('vw-feedback').textContent = f.t
+        ? '\u201c' + f.t + '\u201d'
+        : 'No public feedback shared yet.';
 
       showOnly(viewBox);
       openPanel();