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/mem0/agent_framework_mem0/_context_provider.py

@@ -14,7 +14,6 @@ from typing import TYPE_CHECKING, Any, ClassVar
 
 from agent_framework import Message
 from agent_framework._sessions import AgentSession, BaseContextProvider, SessionContext
-from agent_framework.exceptions import ServiceInitializationError
 from mem0 import AsyncMemory, AsyncMemoryClient
 
 if sys.version_info >= (3, 11):
@@ -172,9 +171,7 @@ class Mem0ContextProvider(BaseContextProvider):
     def _validate_filters(self) -> None:
         """Validates that at least one filter is provided."""
         if not self.agent_id and not self.user_id and not self.application_id:
-            raise ServiceInitializationError(
-                "At least one of the filters: agent_id, user_id, or application_id is required."
-            )
+            raise ValueError("At least one of the filters: agent_id, user_id, or application_id is required.")
 
     def _build_filters(self) -> dict[str, Any]:
         """Build search filters from initialization parameters."""