Add upload response status logging to handleImageUpload

Help diagnose why uploads succeed but show "Upload failed" error.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/core/src/visual-editing/toolbar.ts

@@ -1241,8 +1241,10 @@ export function renderToolbar(config: ToolbarConfig): string {
       });
     })
     .then(function(r) {
+      console.log("[emdash] Upload response status:", r.status);
       if (!r.ok) {
         return r.json().then(function(e) {
+          console.log("[emdash] Upload error response:", JSON.stringify(e));
           var msg = (e && e.error && e.error.message) ? e.error.message : ("Upload failed: " + r.status);
           throw new Error(msg);
         });