Canvas: uploading a reference starts a clean edit (clear preset boxes/prompt, hide hint)

app.py

@@ -568,7 +568,7 @@ SCRIPT = r"""
   }
   function renderAll(){ layoutBoard(); renderBoxes(); renderSummary(); renderTable(); renderSteps();
     NS.el.ratioChips.forEach(c=>c.classList.toggle('sel', c.dataset.r===S.aspect));
-    const hint=NS.el.board.querySelector('.hint'); if(hint) hint.style.display=(!S.rendered && S.elements.length===0)?'flex':'none';
+    const hint=NS.el.board.querySelector('.hint'); if(hint) hint.style.display=(!S.rendered && !S.refImage && S.elements.length===0)?'flex':'none';
     syncState(); }
   function esc(s){return (s||'').replace(/[&<>]/g,m=>({'&':'&amp;','<':'&lt;','>':'&gt;'}[m]));}
 
@@ -652,7 +652,12 @@ SCRIPT = r"""
     if(NS.el.refBox) NS.el.refBox.classList.remove('has');
   }
   function setRef(uri,w,h){
+    // Uploading a reference starts a clean edit: drop any preset scene/boxes so the
+    // user draws fresh regions on their own image.
     S.refImage=uri; S.refW=w; S.refH=h; S.rendered=false; sel=null;
+    S.elements=[]; S.scene=""; S.step=2;
+    if(NS.el.scene) NS.el.scene.value="";
+    (NS.el.exCards||[]).forEach(t=>t.classList.remove('active'));
     const img=NS.el.board.querySelector('img'); if(img)img.remove();
     NS.el.board.classList.remove('rendered','hideboxes'); NS.el.toggleBtn.style.display='none';
     if(NS.el.refThumb) NS.el.refThumb.style.backgroundImage='url('+uri+')';