Yeah, I did see that thread, which led me to look at the security block.
I can see that the assemblyLocator is finding my assembly, but the filter is filtering it out. I'm stepping through this bit of EnsureCommands in the MenuCommandService:
var globalAssemblyCommands = this.assemblyLocator.Assemblies
.FilterSelectManySafe(x => x.GetCustomAttributes(typeof(CommandAttribute), true).OfType<CommandAttribute>())
.Select(x => builder.Resolve(x.CommandModelType, new DependencyOverride(x.GetType(), x)))
I am likely missing the bit about what to attribute with the CommandAttribute.
Thanks a lot for replying Sarah and for any thoughts you may have!