fix(BUILD_ERROR): add gunUtils.js directly to space root

gunUtils.js

@@ -0,0 +1,19 @@
+/**
+ * Sanitize a plain object before passing to Gun.js .put().
+ *
+ * Gun's SEA/YSON layer cannot handle:
+ *   - null property values  → dropped (Gun treats stored null as "delete node")
+ *   - undefined properties  → dropped
+ *   - Array values          → serialized to JSON string (Gun is a graph, not array-friendly)
+ *
+ * Usage:  db.get("papers").get(id).put(gunSafe({ title, lean_proof: null, tags: [] }));
+ */
+export function gunSafe(data) {
+  if (!data || typeof data !== "object" || Array.isArray(data)) return {};
+  const out = {};
+  for (const [key, val] of Object.entries(data)) {
+    if (val === undefined || val === null) continue;
+    out[key] = Array.isArray(val) ? JSON.stringify(val) : val;
+  }
+  return out;
+}