Update @tool to return an AgentTool that also acts as a function (#258)

Right now when you decorate a function you get back another function that mimics the behavior of a python module. Going forward, we're discussing adding helper/utility methods for AgentTool and in anticipatation of those changes return an AgentTool implementation that also acts like the original function.

Co-authored-by: Mackenzie Zastrow <[email protected]>

Author: zastrowm

pyproject.toml

@@ -192,6 +192,7 @@ test-integ = [
 prepare = [
     "hatch fmt --linter",
     "hatch fmt --formatter",
+    "hatch run test-lint",
     "hatch test --all"
 ]
 test-a2a = [