Add more presets to the system prompt

[jerbob92]

Currently, the only preset is claude_code, I do not want to use the claude_code preset, but I do want to be able to use parts of it, for example the part that instructs the auto memory.

It is also pretty unclear what is in the claude_code preset, to give a good understanding of what should be added to a custom prompt to get certain behavior to work correctly (such as auto memory).

My proposal would be to split up parts of the claude_code preset into smaller presets and the ability to construct your own, for example:

system_prompt={
  "type": "preset", 
  "presets": ["formatting_guidelines", "auto_memory", "safety_instructions"],
  "append": "You are a custom agent"
}