`tool-call`: Phi-4 support
- Add system message if needed (per template requirement)
- Add tools to system message (req'd by template)
- Parse output:
-- add tools to response when there is valid JSON between <|tool_call|> and </|tool_call|>
-- content outside of tool_call tags is added to the text portion of the response
-- if there is no valid JSON, the entire content is added to the text portion of the response
