Ensure CLI prompt history directory and file exist before usage (#1707)

Co-authored-by: Zac <2215540+zboyles@users.noreply.github.com>

Author: zboyles

pydantic_ai_slim/pydantic_ai/_cli.py

@@ -203,6 +203,10 @@ def cli(args_list: Sequence[str] | None = None, *, prog_name: str = 'pai') -> in
             pass
         return 0
 
+    # Ensure the history directory and file exist
+    PROMPT_HISTORY_PATH.parent.mkdir(parents=True, exist_ok=True)
+    PROMPT_HISTORY_PATH.touch(exist_ok=True)
+
     # doing this instead of `PromptSession[Any](history=` allows mocking of PromptSession in tests
     session: PromptSession[Any] = PromptSession(history=FileHistory(str(PROMPT_HISTORY_PATH)))
     try: