Python: Add declarative workflow runtime (#2815)

* Further support for declarative python workflows

* Add tests. Clean up for typing and formatting

* Improvements and cleanup

* Typing cleanup. Improve docstrings

* Proper code in docstrings

* Fix malformed code-block directive in docstring

* Remove dead links

* PR feedback

* Address PR feedback

* Address PR feedback

* Remove sl

* Update devui frontend

* More cleanup

* Fix uv lock

* Skip Py 3.14 tests as powerfx doesn't support it

* Fix mypy error

* Fix for tool calls

* Removed stale docstring

* Fix lint

* Standardize on .NET namespaces. Revert DevUI changes (bring in later)

* Implement remaining items for Python declarative support to match dotnet

python/samples/getting_started/devui/declarative/__init__.py

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+# Copyright (c) Microsoft. All rights reserved.
+
+"""Declarative workflow sample for DevUI."""

python/samples/getting_started/devui/declarative/workflow.py

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+# Copyright (c) Microsoft. All rights reserved.
+
+"""
+Run the declarative workflow sample with DevUI.
+
+Demonstrates conditional branching based on age input using YAML-defined workflow.
+"""
+
+from pathlib import Path
+
+from agent_framework.declarative import WorkflowFactory
+from agent_framework.devui import serve
+
+factory = WorkflowFactory()
+workflow_path = Path(__file__).parent / "workflow.yaml"
+workflow = factory.create_workflow_from_yaml_path(workflow_path)
+
+
+def main():
+    """Run the declarative workflow with DevUI."""
+    serve(entities=[workflow], auto_open=True)
+
+
+if __name__ == "__main__":
+    main()

python/samples/getting_started/devui/declarative/workflow.yaml

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+name: conditional-workflow
+description: Demonstrates conditional branching based on user input
+
+inputs:
+  age:
+    type: integer
+    description: The user's age in years
+
+actions:
+  - kind: SetValue
+    id: get_age
+    displayName: Get user age
+    path: turn.age
+    value: =inputs.age
+
+  - kind: If
+    id: check_age
+    displayName: Check age category
+    condition: =turn.age < 13
+    then:
+      - kind: SetValue
+        path: turn.category
+        value: child
+      - kind: SendActivity
+        activity:
+          text: "Welcome, young one! Here are some fun activities for kids."
+    else:
+      - kind: If
+        condition: =turn.age < 20
+        then:
+          - kind: SetValue
+            path: turn.category
+            value: teenager
+          - kind: SendActivity
+            activity:
+              text: "Hey there! Check out these cool things for teens."
+        else:
+          - kind: If
+            condition: =turn.age < 65
+            then:
+              - kind: SetValue
+                path: turn.category
+                value: adult
+              - kind: SendActivity
+                activity:
+                  text: "Welcome! Here are our professional services."
+            else:
+              - kind: SetValue
+                path: turn.category
+                value: senior
+              - kind: SendActivity
+                activity:
+                  text: "Welcome! Enjoy our senior member benefits."
+
+  - kind: SendActivity
+    id: summary
+    displayName: Send category summary
+    activity:
+      text: '=Concat("You have been categorized as: ", turn.category)'
+
+  - kind: SetValue
+    id: set_output
+    path: workflow.outputs.category
+    value: =turn.category