> That project's META-INF/beans.xml has bean discovery set to none
> (https://github.com/ljnelson/microbean-main/blob/master/src/main/resources/META-INF/beans.xml#L7),
> since there are no beans in that bean archive (it houses only the main
> class).  John indicated that this was likely the source of the problem:

I don't think this is the problem. In Weld SE bean archive isolation is
enabled by default. Ie. for
https://github.com/ljnelson/microbean-maven-cdi/blob/master/src/main/java/org/microbean/maven/cdi/MavenExtension.java
the beans.xml is
https://github.com/ljnelson/microbean-maven-cdi/blob/master/src/main/resources/META-INF/beans.xml

> Perhaps I have misunderstood bean discovery: I thought that the
> discovery mode applied to the bean archive in question alone, not to an
> aggregate.

What do you mean with "aggregate"? Bean discovery mode is applied to a
specific bean archive only.