I think the model should only know about spotting some kind of token the LLM has the order to give when it doesn't know something related to your personal taste.
It is technically possible (I insist on technically) for the LLM to be moderated in such a way that it retains itself from hallucinating your personal tastes, in the same way it is actually possible for gpt models to give answers such as "As a trained language model, I cannot blablabla" when certain conditions are met.
From here, you have to imagine the scratch pad to be a sort of manual file you have the responsability to feed in order for the LLM to have the necessary context to answer your request. The sidekick model is there only to trigger the condition "something must be added to the scratch pad, due to the appearance of a certain token in the LLM response".
I can imagine building something like this in emacs, where a buffer containing the scratch pad is opened on the sidekick demand :
you have the responsability to enter "Bob's favourite song is X", or maybe the sidekick is able to extract elements of the LLM answer to propose " The LLM failed to answer when you asked, as user Y : What is my favourite song ?".
The sidekick can be very simple as I said, this depends on the ability for your LLM to be moderated.
GPT4's answer to the "What is my favourite song ?" :
I don't have access to personal data about someone unless it has been shared with me in the course of our conversation. I am designed to respect user privacy. So, I don't know what your favorite song is unless you tell me. What is it?
I can add instructions to every prompt I perform so that GPT4 says "Please input X" when it lacks X information about me to answer.
Hello, what's my favourite song ?
Answer:
Please input your favourite song:
The middleware recognize the form "Please input X", opens the scratchpad buffer, adds :
Favourite song:
And you type your favourite song here.
The scratchpad may have some kind of sentence like " Here is a list of things about me you should remember." That helps contextualizing content for the LLM.