fix: prevent config clobbering

src/config/merge-patch.ts

@@ -0,0 +1,28 @@
+type PlainObject = Record<string, unknown>;
+
+function isPlainObject(value: unknown): value is PlainObject {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+export function applyMergePatch(base: unknown, patch: unknown): unknown {
+  if (!isPlainObject(patch)) {
+    return patch;
+  }
+
+  const result: PlainObject = isPlainObject(base) ? { ...base } : {};
+
+  for (const [key, value] of Object.entries(patch)) {
+    if (value === null) {
+      delete result[key];
+      continue;
+    }
+    if (isPlainObject(value)) {
+      const baseValue = result[key];
+      result[key] = applyMergePatch(isPlainObject(baseValue) ? baseValue : {}, value);
+      continue;
+    }
+    result[key] = value;
+  }
+
+  return result;
+}