feat: show error text in chat output

public/index.html

@@ -366,11 +366,15 @@
               fullText += obj.text;
               outputEl.innerHTML = renderMarkdown(fullText);
               outputEl.scrollTop = outputEl.scrollHeight;
+            } else if (obj.error) {
+              outputEl.innerHTML = '<span style="color:#f55">' + obj.error + '</span>';
             }
           } catch(e) {}
         }
       }
-    } catch(e) {} finally { inFlight = false; }
+    } catch(e) {
+      outputEl.innerHTML = '<span style="color:#f55">fetch error: ' + e.message + '</span>';
+    } finally { inFlight = false; }
   }
 
   // Auto-send on paste — all images + all text in one clipboard event go as ONE request