Move pydantic_base.py to src/a2a/

Author: holtskinner

.github/workflows/update-a2a-types.yml

@@ -9,6 +9,8 @@ on:
       - main
     paths:
       - "scripts/generate_types.sh"
+      - "src/a2a/types.py"
+      - "src/pydantic_base.py"
     types:
       - opened
       - synchronize