4.0: runtime scope errors should be ResolutionErrors #562

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

Observation

docs/providers/errors-and-exceptions.md:101 says "Catch ResolutionError for any resolution failure", but ScopeNotInitializedError, ScopeSkippedError and ContainerClosedError subclass ContainerError (modern_di/exceptions/container.py:50,69,102). So except ResolutionError misses root.resolve(RequestScoped) and a resolve from a closed container.

Related: InvalidScopeDependencyError (exceptions/registration.py:168) subclasses RegistrationError, a module documented as "while providers and groups are declared", but it is raised by validate() (dependency_graph.py:197), so except RegistrationError catches a validation finding.

Changing a base class after 4.0 changes which except clauses fire, so it is a 5.0 change later and cheap now.

Proposal

• Re-parent the three runtime errors under ResolutionError (they already carry DependencyPathMixin). Decide whether ContainerError stays a second base for them or is reserved for construction-time errors (InvalidChildScopeError, MaxScopeReachedError, InvalidScopeTypeError).
• Decide the family of InvalidScopeDependencyError (validation, not registration).
• Update errors-and-exceptions.md and the migration guide.

Acceptance

• except ResolutionError catches every error raised from resolve/resolve_provider, with a test per error type.
• Hierarchy table in the docs matches the code; migration guide has an entry.