Python: [BREAKING] Redesign Python exception hierarchy (#4082)

* [BREAKING] Redesign Python exception hierarchy

Replace the flat ServiceException family with domain-scoped branches:
- AgentException (with InvalidAuth, InvalidRequest, InvalidResponse, ContentFilter)
- ChatClientException (same consistent suberrors)
- IntegrationException (same + InitializationError)
- WorkflowException (Runner, Convergence, Checkpoint, Validation, Action, Declarative)
- ContentError (AdditionItemMismatch)
- ToolException / ToolExecutionException (unchanged)
- MiddlewareException / MiddlewareTermination (unchanged)

Key changes:
- All Service* exceptions removed (ServiceException, ServiceInitializationError, etc.)
- AgentExecutionException split into AgentInvalidRequest/ResponseException
- AgentInvocationError removed, split into AgentInvalidRequest/ResponseException
- Workflow exceptions moved from _workflows/_exceptions.py into main exceptions.py
- _workflows/__init__.py emptied; main __init__.py imports directly from submodules
- Purview exceptions re-parented under IntegrationException hierarchy
- Init validation errors use built-in ValueError/TypeError instead of custom exceptions
- CODING_STANDARD.md updated with hierarchy design and rationale

Fixes microsoft/agent-framework#3410

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Clarify ToolException vs ToolExecutionException docstrings

ToolException: base class for all tool-related exceptions (preconditions,
connection/init failures).
ToolExecutionException: runtime call failures (tool call failed, reconnect
failed, MCP errors).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix remaining stale imports from agent_framework._workflows

- azurefunctions: _context.py, _app.py, _serialization.py, test_func_utils.py
  used 'from agent_framework._workflows import X' which broke after
  emptying _workflows/__init__.py; changed to direct submodule imports
- azure-ai-search: test still referenced ServiceInitializationError;
  updated to ValueError to match production code

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

python/packages/ag-ui/agent_framework_ag_ui/_run.py

@@ -40,7 +40,7 @@ from agent_framework._tools import (
     normalize_function_invocation_configuration,
 )
 from agent_framework._types import ResponseStream
-from agent_framework.exceptions import AgentExecutionException
+from agent_framework.exceptions import AgentInvalidResponseException
 
 from ._message_adapters import normalize_agui_input_messages
 from ._orchestration._predictive_state import PredictiveStateHandler
@@ -207,7 +207,7 @@ async def _normalize_response_stream(response_stream: Any) -> AsyncIterable[Any]
         if isinstance(resolved_stream, AsyncIterable):
             return cast(AsyncIterable[Any], resolved_stream)
         resolved_type = f"{type(resolved_stream).__module__}.{type(resolved_stream).__name__}"
-        raise AgentExecutionException(
+        raise AgentInvalidResponseException(
             "Agent did not return a streaming AsyncIterable response. "
             f"Awaitable resolved to unsupported type: {resolved_type}."
         )
@@ -220,7 +220,7 @@ async def _normalize_response_stream(response_stream: Any) -> AsyncIterable[Any]
         return cast(AsyncIterable[Any], response_stream)
 
     stream_type = f"{type(response_stream).__module__}.{type(response_stream).__name__}"
-    raise AgentExecutionException(
+    raise AgentInvalidResponseException(
         f"Agent did not return a streaming AsyncIterable response. Received unsupported type: {stream_type}."
     )
 

python/packages/ag-ui/tests/ag_ui/test_run.py

@@ -8,7 +8,7 @@ from ag_ui.core import (
     TextMessageStartEvent,
 )
 from agent_framework import AgentResponseUpdate, Content, Message, ResponseStream
-from agent_framework.exceptions import AgentExecutionException
+from agent_framework.exceptions import AgentInvalidResponseException
 
 from agent_framework_ag_ui._run import (
     FlowState,
@@ -226,7 +226,7 @@ class TestNormalizeResponseStream:
 
     async def test_rejects_non_stream_values(self):
         """Reject unsupported stream return values."""
-        with pytest.raises(AgentExecutionException):
+        with pytest.raises(AgentInvalidResponseException):
             await _normalize_response_stream("not-a-stream")