feat: Consolidate and subdivide rules

[MikkelPaulson]

This is a draft implementation of #463 for review and discussion. See the parent issue for the schema proposal.

To do:

• [x] Migrate data to new schema
• [ ] Update API & docs (I presume)
• [ ] Add test coverage to detect orphans, circular references, and contradictory parent/child relationships
• [ ] Delete Python script before merging (included for discussion)

[bagelbits]

I think that looks good if you want to go forward with the rest.