Add a chat interface

[cmungall]

The current way of interacting with the app is incredibly clunky - multiple selectors on the left, confusing, easy to select the wrong thing

It should be a chat interface like @oneilsh's PA interface

There could be power-user CLI commands that bypass GPT, e.g.

• !ont_hp/search liver phenotype
• !ont_envo/chat[gpt4] what are volcanoes?
• !maxoa/extract PMID:123456

But anything else should be passed to a model and use ReAct to trigger appropriate action