You have described dame's rocket or sweet rocket. I ordered some that was not fragrant. Ask on the seed exchange for seeds from fragrant plants.

That is not it.

Mine was more of a rounded bush, with less stemmy flowers, more short branches, and pale flowers, purple like wild radish. The leaves were also much paler

Maybe a Wallflower (Erysimum)?

No but thanks for trying

The flowers were more single to each branch, not clusters

How about Clerodendron bungei. Purple mustard looking flowers, foliage weedy, with very fragrant flowers. Al

Thanks for trying Al but that is not it. I think I will try googleing Annies annuals

OK

The Annie's Annual staff helped me find it,Matthiola bicornis