Command topic producer should use EXACTLY ONCE.

Currently, by default exactly once is not set for the producer for the command topic. This can result in corner cases where we have duplicate commands in the command topic. We should set the producer for the command topic to use exactly once.

Start by tracing the producer used for the command topic and inspect how its delivery settings are configured. Confirm the intended exactly-once setting and add or update coverage for duplicate-command behavior; done means command-topic production uses exactly once by default.

Written by the indexing model from the issue text.