feat: add custom guidance to summarize_when_long hook

Key Changes:

• suggestion PR enhances summarize_when_long hook with a customizable prompt appended

• The base prompt defines the structure and format

• If you provide guidance, rigging injects it as additional instructions

• The model follows both: the structure and custom guidance

  Example usage:

  summarize_when_long(
      model="groq/openai/gpt-oss-120b",
      max_tokens=80000,
      min_messages_to_keep=2,
      guidance="Focus on security testing: vulnerability findings, exploit payloads, HTTP evidence, and verifier confirmations."
  )

Changed:

• Updates to existing hook

Generated Summary:

• Introduced a new optional parameter guidance to the summarize_when_long function for enhanced control over the summarization process.
• Updated the function docstring to include details about the new guidance parameter.
• Modified the configuration to allow setting of the guidance parameter with a default value of an empty string.
• Passed the guidance parameter during the summary generation call to the summarize_conversation function.
• These changes enhance the flexibility and effectiveness of the conversation summarization feature.

This summary was generated with ❤️ by rigging