feat(mockup): add OpenAI Codex (gpt-5.6-sol + built-in image_gen) raster mockup generator

public/app.js

@@ -1803,7 +1803,7 @@ function bindGlobalEvents() {
     const editInstruction = document.getElementById("nb-edit-instruction-input").value.trim();
 
     btn.disabled = true;
-    statusLabel.textContent = "🍌 Calling Nano Banana 2.1 (gemini-nano-banana-2.1)...";
+    statusLabel.textContent = "🎨 Generating high-res AI mockup via OpenAI Codex (takes ~15–25s)...";
 
     try {
       const res = await apiFetch(`/api/ideas/${state.activeIdeaId}/mockups/nano-banana`, {