Python: [Breaking] Remove WorkflowCompletedEvent, introduce workflow output and migrate to ctx.yield_output() + a huge refactoring (#845)

* Introduce input and output types for executor and workflow

* WorkflowOutputContext handles two types

* Remove can_handle_types from Executor

* Update validation

* Move workflow executor

* Move workflow executor

* Fix issues in WorkflowExecutor

* refactor executor

* update execute signature to create workflow context within Executor

* fix simple sub workflow test; fix validation

* fix output types in WorkflowExecutor

* fix issue in Executor handling of SubWorkflowRequestInfo

* update tests to use proper workflow output

* update orchestration patterns to use output

* Update sample -- not finished

* Update python/packages/main/tests/workflow/test_workflow_states.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update python/packages/main/tests/workflow/test_concurrent.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* address comments

* WorkflowOutputContext --> WorkflowContext

* remove WorkflowCompletedEvent

* update samples

* Update doc string for important classes; update WorkflowExecutor to support concurrent execution

* use Never instead of None for default type

* Update usage of WorkflowContext[None to WorkflowContext[Never

* address comments

* remove filter for None

* address comments, minor fixes

* quality of life improvement on interceptor types

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

python/packages/main/tests/workflow/test_validation.py

@@ -19,7 +19,6 @@ from agent_framework import (
     validate_workflow_graph,
 )
 from agent_framework._workflow._edge import SingleEdgeGroup
-from agent_framework._workflow._validation import HandlerOutputAnnotationError
 
 
 class StringExecutor(Executor):
@@ -51,8 +50,8 @@ class AnyExecutor(Executor):
 
 class NoOutputTypesExecutor(Executor):
     @handler
-    async def handle_message(self, message: str, ctx: WorkflowContext[Any]) -> None:
-        await ctx.send_message("processed")
+    async def handle_message(self, message: str, ctx: WorkflowContext) -> None:
+        await ctx.send_message("processed")  # type: ignore[arg-type]
 
 
 class MultiTypeExecutor(Executor):
@@ -575,58 +574,33 @@ def test_validation_enum_usage() -> None:
 
 
 def test_handler_ctx_missing_annotation_raises() -> None:
-    class BadExecutor(Executor):
-        @handler
-        async def handle(self, message: str, ctx) -> None:  # type: ignore[no-untyped-def]
-            pass
+    # Validation now happens at handler registration time, not workflow build time
+    with pytest.raises(ValueError) as exc:
 
-    start = StringExecutor(id="s")
-    bad = BadExecutor(id="b")
+        class BadExecutor(Executor):
+            @handler
+            async def handle(self, message: str, ctx) -> None:  # type: ignore[no-untyped-def]
+                pass
 
-    with pytest.raises(HandlerOutputAnnotationError) as exc:
-        WorkflowBuilder().add_edge(start, bad).set_start_executor(start).build()
-
-    assert exc.value.validation_type == ValidationTypeEnum.HANDLER_OUTPUT_ANNOTATION
-    assert "missing type annotation" in str(exc.value)
-
-
-def test_handler_ctx_unsubscripted_workflow_context_raises() -> None:
-    class BadExecutor(Executor):
-        @handler
-        async def handle(self, message: str, ctx: WorkflowContext) -> None:  # type: ignore # missing T
-            pass
-
-    start = StringExecutor(id="s")
-    bad = BadExecutor(id="b")
-
-    with pytest.raises(HandlerOutputAnnotationError) as exc:
-        WorkflowBuilder().add_edge(start, bad).set_start_executor(start).build()
-
-    assert exc.value.validation_type == ValidationTypeEnum.HANDLER_OUTPUT_ANNOTATION
-    # Message should mention missing T or WorkflowContext[None]
-    assert "WorkflowContext[None]" in str(exc.value) or "missing" in str(exc.value).lower()
+    assert "must have a WorkflowContext" in str(exc.value)
 
 
 def test_handler_ctx_invalid_t_out_entries_raises() -> None:
-    class BadExecutor(Executor):
-        @handler
-        async def handle(self, message: str, ctx: WorkflowContext[123]) -> None:  # type: ignore[valid-type]
-            pass
+    # Validation now happens at handler registration time, not workflow build time
+    with pytest.raises(ValueError) as exc:
 
-    start = StringExecutor(id="s")
-    bad = BadExecutor(id="b")
+        class BadExecutor(Executor):
+            @handler
+            async def handle(self, message: str, ctx: WorkflowContext[123]) -> None:  # type: ignore[valid-type]
+                pass
 
-    with pytest.raises(HandlerOutputAnnotationError) as exc:
-        WorkflowBuilder().add_edge(start, bad).set_start_executor(start).build()
-
-    assert exc.value.validation_type == ValidationTypeEnum.HANDLER_OUTPUT_ANNOTATION
-    assert "invalid entries" in str(exc.value)
+    assert "invalid type entry" in str(exc.value)
 
 
 def test_handler_ctx_none_is_allowed() -> None:
     class NoneExecutor(Executor):
         @handler
-        async def handle(self, message: str, ctx: WorkflowContext[None]) -> None:
+        async def handle(self, message: str, ctx: WorkflowContext) -> None:
             # does not emit
             return None