[DOC] Update PER Agent documentation with new features

[pyek-bot]

What do you want to do?

• Request a change to existing documentation
• Add new documentation
• Report a technical problem with the documentation
• Other

Update PER Agent documentation with the below:

• Fix the client_config error (the API here is wrong)
• Talk about date injection
• Mention the changes to the prompts
• Talk about message_history limit now being parameterized

Version:
3.2