Error chains: wrong argument named, missing step for ContextProvider #570

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

1. Context error raised inside a creator body names the outer argument

Inner.__init__(self, c: Container) calls c.resolve(Tenant) (unset context); Outer(inner: Inner). Resolving Outer reports arg_name='inner', "needed for argument inner", and the chain lacks the Inner step. The except ContextValueNotSetError branch in the _TRANSIENT/_CACHED templates (resolver_compiler.py) names by tb_lineno of the frame it is in, but the error came from a nested resolve that already passed its own frame. Expected: the argument/step of the innermost resolver that raised; an error that already has arg_name set is not renamed.

2. Directly resolving a ContextProvider from too shallow a container has no step

resolver_compiler.py:277 calls find_container directly instead of _navigate, so the scope error names no provider, unlike Factory.

Acceptance

Failing tests first for both; message text checked.