Earlier quoted context omitted.
Isn’t that what the agents.md in your project is for?
Depends on how much information and details you have. The agents.md always goes into context. Detailed testing or process information might be excessive, when agent is working on UI. Skills are pulled when needed.
This documentation is its own git repo, and the agents.md file has an explicit instruction to update the docs when it has learned something general that can be useful in future sessions. I then occasionally review and prune those docs.