fix: fix incorrect strict-recovery in `get_tool_messages(str)`
Extends the fix in 758 to string-typed calls to get_tool_messages for ChatAgents
by ensuring that the recovery flag is sent only when one of the following is true:
- the most recent message in the history was produced by the LLM, or
- the argument is a ChatDocument sent by the LLM.
Resolves 753
Thanks nilspalumbo!