* initial model store
* refactor the 'modelstoreserviceimpl' to pinia
* pepper in some reactive
the inner ModelStore (per-folder) can't be pinia because its made of temporary instances, but it can be reactive
* use refs in metadata class
* remove 'reactive'
* remove ref too
* add simple unit tests for modelStore
* make things worse via autoformatting
* move mock impls to a function
