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/bedrock/agent_framework_bedrock/_chat_client.py

@@ -30,7 +30,7 @@ from agent_framework import (
     validate_tool_mode,
 )
 from agent_framework._settings import SecretString, load_settings
-from agent_framework.exceptions import ServiceInitializationError, ServiceInvalidResponseError
+from agent_framework.exceptions import ChatClientInvalidResponseException
 from agent_framework.observability import ChatTelemetryLayer
 from boto3.session import Session as Boto3Session
 from botocore.client import BaseClient
@@ -362,13 +362,13 @@ class BedrockChatClient(
     ) -> dict[str, Any]:
         model_id = options.get("model_id") or self.model_id
         if not model_id:
-            raise ServiceInitializationError(
+            raise ValueError(
                 "Bedrock model_id is required. Set via chat options or BEDROCK_CHAT_MODEL_ID environment variable."
             )
 
         system_prompts, conversation = self._prepare_bedrock_messages(messages)
         if not conversation:
-            raise ServiceInitializationError("At least one non-system message is required for Bedrock requests.")
+            raise ValueError("At least one non-system message is required for Bedrock requests.")
         # Prepend instructions from options if they exist
         if instructions := options.get("instructions"):
             system_prompts = [{"text": instructions}, *system_prompts]
@@ -400,7 +400,7 @@ class BedrockChatClient(
                     else:
                         tool_config["toolChoice"] = {"any": {}}
                 case _:
-                    raise ServiceInitializationError(f"Unsupported tool mode for Bedrock: {tool_mode.get('mode')}")
+                    raise ValueError(f"Unsupported tool mode for Bedrock: {tool_mode.get('mode')}")
         if tool_config:
             run_options["toolConfig"] = tool_config
 
@@ -629,7 +629,9 @@ class BedrockChatClient(
             if isinstance(tool_use, MutableMapping):
                 tool_name = tool_use.get("name")
                 if not tool_name:
-                    raise ServiceInvalidResponseError("Bedrock response missing required tool name in toolUse block.")
+                    raise ChatClientInvalidResponseException(
+                        "Bedrock response missing required tool name in toolUse block."
+                    )
                 contents.append(
                     Content.from_function_call(
                         call_id=tool_use.get("toolUseId") or self._generate_tool_call_id(),

python/packages/bedrock/tests/test_bedrock_client.py

@@ -6,7 +6,6 @@ from typing import Any
 
 import pytest
 from agent_framework import Content, Message
-from agent_framework.exceptions import ServiceInitializationError
 
 from agent_framework_bedrock import BedrockChatClient
 
@@ -64,5 +63,5 @@ def test_build_request_requires_non_system_messages() -> None:
 
     messages = [Message(role="system", contents=[Content.from_text(text="Only system text")])]
 
-    with pytest.raises(ServiceInitializationError):
+    with pytest.raises(ValueError):
         client._prepare_options(messages, {})