Link Chemiscope load param to dataset json

app.py

@@ -319,16 +319,26 @@ def _build_chemiscope_embed(dataset_payload: dict, dataset_path: str | Path) ->
     viewer_path = dataset_file.parent / viewer_name
     viewer_path.write_text(combined, encoding="utf-8")
 
-    view_rel_path = viewer_path.as_posix()
+    space_origin = _infer_space_origin()
+    if space_origin:
+        dataset_url = f"{space_origin}/file={dataset_file.as_posix()}"
+        load_param = urllib.parse.quote(dataset_url, safe=":/?=&%")
+        iframe_src = f"https://chemiscope.org/?load={load_param}"
+        link = iframe_src
+    else:
+        encoded = base64.b64encode(combined.encode("utf-8")).decode("ascii")
+        iframe_src = f"data:text/html;base64,{encoded}"
+        link = iframe_src
+
     return (
         "<div style='width:100%;'>"
         "<iframe "
         "title='Chemiscope explorer' "
         "style='width:100%;height:620px;border:none;border-radius:8px;' "
-        f"src='https://chemiscope.org/?load={urllib.parse.quote(view_rel_path)}'></iframe>"
+        f"src='{iframe_src}'></iframe>"
         "<p style='font-size:0.9em;margin-top:0.5rem;'>"
         "Open in a new tab if the viewer looks blank: "
-        f"<a href='https://chemiscope.org/?load={urllib.parse.quote(view_rel_path)}' target='_blank' rel='noopener'>Chemiscope standalone</a>"
+        f"<a href='{link}' target='_blank' rel='noopener'>Chemiscope standalone</a>"
         "</p>"
         "</div>"
     )