4.0: consistent exception attributes and exports

This was generated by AI during a pre-4.0 audit of main at 9cd88e7.

Observation

Parameter names: arg_name (ArgumentResolutionError, ContextValueNotSetError) vs parameter_name (UnsupportedCreatorParameterError, InvalidScopeDependencyError).
ContextValueNotSetError.__init__(scope_name: str) (exceptions/resolution.py:181) takes a string; every other scope-bearing error stores an IntEnum (provider_scope, container_scope, scope).
ArgumentResolutionError(bound_type=...) also receives the creator callable when there is no bound type (providers/factory.py:158), and member_types is accepted but not stored, unlike arg_type (exceptions/resolution.py:65-77).
exceptions.__all__ exports DependencyPathMixin and SUGGESTION_HEADER, which have no use outside the package (exceptions/__init__.py).
AliasSourceNotRegisteredError still says "Register a provider for X before defining the alias" (exceptions/resolution.py:54); since perf(alias): bind an Alias to its source at compile time #559 the source only has to be registered before the first resolve.

One parameter attribute name across exceptions.
ContextValueNotSetError(scope: IntEnum); render .name.
Split ArgumentResolutionError.bound_type into bound_type and creator; store member_types.
Drop DependencyPathMixin and SUGGESTION_HEADER from __all__.
Fix the alias message.
Migration guide entries for every renamed attribute.

Tests assert the new attributes; rendered messages unchanged except the alias one; docs and migration guide updated.