Show structured inference errors

index.html

@@ -131,7 +131,12 @@
             stream: true,
           }),
         });
-        if (!response.ok) throw new Error((await response.text()) || `HTTP ${response.status}`);
+        if (!response.ok) {
+          const errorBody = await response.text();
+          let message = errorBody;
+          try { message = JSON.parse(errorBody).error?.message || errorBody; } catch {}
+          throw new Error(message || `HTTP ${response.status}`);
+        }
 
         const reader = response.body.getReader();
         const decoder = new TextDecoder();