Re-inject Character system prompts and instructions

The biggest flaw with the Characters system is that the LLM ends up completely forgetting who it is meant to be the longer the discussion goes on. The system prompt and instructions seem to be injected on the very first message, and then buried in the chat log and the character just ceases to have their personality, which is the entire point of Characters.

Characters having their system prompts and instructions reminded to them automatically before each response would improve the system drastically.