Fix viewer overlay state hiding the reconstructed iframe

After a successful reconstruction, the pipeline called
setViewerState('idle') — which shows the "Ready / Upload an image"
overlay on top of the iframe. The overlay covered the loaded 3D scene,
making it look stuck.

Add a 'ready' state that hides every overlay and reveals the iframe.
Use 'ready' at both completion points (iframe onload and after HTML
bundling) instead of 'idle'.

app.py

@@ -615,15 +615,26 @@ INDEX_HTML = r"""<!doctype html>
 
     function setViewerState(state, opts) {
       opts = opts || {};
-      viewerIdle.classList.toggle("hidden", state !== "idle");
-      viewerLoading.classList.toggle("hidden", state !== "loading");
-      viewerError.classList.toggle("hidden", state !== "error");
-      if (state === "loading") {
+      const isReady = state === "ready";
+      const isLoading = state === "loading";
+      const isError = state === "error";
+      const isIdle = state === "idle";
+      viewerIdle.classList.toggle("hidden", !isIdle);
+      viewerLoading.classList.toggle("hidden", !isLoading);
+      viewerError.classList.toggle("hidden", !isError);
+      if (isLoading) {
         loadingTitle.textContent = opts.title || "Reconstructing scene";
         loadingDetail.textContent = opts.detail || "Running model inference";
         progressBar.style.width = (opts.progress || 0) + "%";
       }
-      if (state === "error") errorDetail.textContent = opts.detail || "Unknown error";
+      if (isError) errorDetail.textContent = opts.detail || "Unknown error";
+      viewerFrame.classList.toggle("ready", isReady);
+      if (isReady) {
+        // Hide every overlay so the iframe takes the full surface.
+        viewerIdle.classList.add("hidden");
+        viewerLoading.classList.add("hidden");
+        viewerError.classList.add("hidden");
+      }
     }
 
     function setReady(ready) {
@@ -744,7 +755,7 @@ INDEX_HTML = r"""<!doctype html>
         viewerFrame.src = viewerUrl;
         viewerFrame.onload = () => {
           viewerFrame.classList.add("ready");
-          setViewerState("idle");
+          setViewerState("ready");
         };
 
         setViewerState("loading", { title: "Bundling HTML", detail: "Embedding assets for download", progress: 92 });
@@ -752,7 +763,7 @@ INDEX_HTML = r"""<!doctype html>
         const htmlUrl = html.data[0].url;
         setDownload(dlHtml, htmlUrl, "Download HTML viewer — Ready");
 
-        setViewerState("idle");
+        setViewerState("ready");
         toastMsg("Reconstruction complete");
       } catch (err) {
         console.error(err);