fix(serenity): restore parent_id: null in updateProjectTag body

The previous fix used `?? undefined` to satisfy TypeScript, but `null ?? undefined`
evaluates to `undefined`, which JSON-serializes as a missing key — breaking the
null-promotion contract. Cast to `any` instead so the null is preserved on the wire
while TypeScript is satisfied.

Introduced by: N/A
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: cboldis

src/support/serenity/rest-transport.js

@@ -581,7 +581,9 @@ export function createSerenityTransport({ env, imsToken }) {
           + 'Pass the tag\'s current parent id to rename in place, or null to promote deliberately.',
         );
       }
-      const body = { name, parent_id: parentId ?? undefined };
+      // parent_id: null is intentional (promotes tag to root); cast needed because the
+      // generated type omits null even though the API accepts it for field-clearing PATCH.
+      const body = /** @type {any} */({ name, parent_id: parentId });
       return unwrap('PATCH', await projects.PATCH(
         '/v2/workspaces/{id}/projects/{project_id}/aio/tags/{tag_id}',
         {