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/ollama/agent_framework_ollama/_chat_client.py

@@ -32,8 +32,8 @@ from agent_framework import (
 )
 from agent_framework._settings import load_settings
 from agent_framework.exceptions import (
-    ServiceInvalidRequestError,
-    ServiceResponseException,
+    ChatClientException,
+    ChatClientInvalidRequestException,
 )
 from agent_framework.observability import ChatTelemetryLayer
 from ollama import AsyncClient
@@ -363,7 +363,7 @@ class OllamaChatClient(
                         **kwargs,
                     )
                 except Exception as ex:
-                    raise ServiceResponseException(f"Ollama streaming chat request failed : {ex}", ex) from ex
+                    raise ChatClientException(f"Ollama streaming chat request failed : {ex}", ex) from ex
 
                 async for part in response_object:
                     yield self._parse_streaming_response_from_ollama(part)
@@ -381,7 +381,7 @@ class OllamaChatClient(
                     **kwargs,
                 )
             except Exception as ex:
-                raise ServiceResponseException(f"Ollama chat request failed : {ex}", ex) from ex
+                raise ChatClientException(f"Ollama chat request failed : {ex}", ex) from ex
 
             return self._parse_response_from_ollama(response)
 
@@ -423,7 +423,7 @@ class OllamaChatClient(
         if messages and "messages" not in run_options:
             run_options["messages"] = self._prepare_messages_for_ollama(messages)
         if "messages" not in run_options:
-            raise ServiceInvalidRequestError("Messages are required for chat completions")
+            raise ChatClientInvalidRequestException("Messages are required for chat completions")
 
         # model id
         if not run_options.get("model"):
@@ -457,7 +457,7 @@ class OllamaChatClient(
 
     def _format_user_message(self, message: Message) -> list[OllamaMessage]:
         if not any(c.type in {"text", "data"} for c in message.contents) and not message.text:
-            raise ServiceInvalidRequestError(
+            raise ChatClientInvalidRequestException(
                 "Ollama connector currently only supports user messages with TextContent or DataContent."
             )
 
@@ -468,7 +468,9 @@ class OllamaChatClient(
         data_contents = [c for c in message.contents if c.type == "data"]
         if data_contents:
             if not any(c.has_top_level_media_type("image") for c in data_contents):
-                raise ServiceInvalidRequestError("Only image data content is supported for user messages in Ollama.")
+                raise ChatClientInvalidRequestException(
+                    "Only image data content is supported for user messages in Ollama."
+                )
             # Ollama expects base64 strings without prefix
             user_message["images"] = [c.uri.split(",")[1] for c in data_contents if c.uri]
         return [user_message]