show glossary definitions inline

Identify terms from the glossary with some kind of decoration (e.g. dotted underline). On hover/click/??? the definition appears.

I don't know if this is necessary, links to the glossary may be sufficient. I'm thinking about terms like "enumerator" or "instance" that we throw around but that may not be familiar to everyone.

Start by reviewing the existing glossary and the Sphinx documentation structure. First decide whether inline definitions are needed instead of glossary links, then define the interaction and decoration; the work is done when the chosen behavior is implemented consistently and its documentation build succeeds.

Written by the indexing model from the issue text.