"ERROR: operation is not allowed on this node" when creating custom type

I am unable to create ENUM type after installing citus columnar extension on PostgreSQL 13.

```
CREATE TYPE company AS ENUM ('test1','test2')

ERROR: operation is not allowed on this node
Hint: Connect to the coordinator and run it again.
1 statement failed.
```
Citus version:
Citus 10.0.3 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 8.3.1 20190311 (Red Hat 8.3.1-3.2.0.1), 64-bit.

The error message states to connect to the coordinator, but coordinator and workers have not been configured since I only need columnar extension.

Start by reproducing CREATE TYPE company AS ENUM after installing Citus 10.0.3 with PostgreSQL 13 and no coordinator or workers configured. Trace the handling of this statement and the coordinator-only error path; done means the issue's expected behavior or a precise limitation is established and covered by an appropriate regression test.

Written by the indexing model from the issue text.