[Context] add learnings from the front

[Westbrook]

Some teams (e.g. the Lit team) have been registering learnings around the Context Protocol of that are not currently included in the documented version. Let’s get those included back via PRs!

Some features I know about:

• lazy context registration
• late changing context hosts
• I’m sure there are more

@justinfagnani can you help get the most up-to-date info on this?