Redesign Python AI engine (#5991)

# Description of Changes
Redesign the Python AI engine to be properly agentic and make use of
`pydantic-ai` instead of `langchain` for correctness and ergonomics.
This should be a good foundation for us to build our AI engine on going
forwards.

engine/src/stirling/models/__init__.py

@@ -0,0 +1,11 @@
+from . import tool_models
+from .base import ApiModel
+from .tool_models import OPERATIONS, OperationId, ParamToolModel
+
+__all__ = [
+    "ApiModel",
+    "OPERATIONS",
+    "OperationId",
+    "ParamToolModel",
+    "tool_models",
+]