0.7.0

Changed

• Replace the Opaque marker trait with the RustSpec::Opacity = Opaque | NonOpaque axis.
• Reject raw pointer fields in non-opaque derives and conflicting opaque attributes.

Fixed

• Classify raw pointers and NonNull according to the pointee's metadata shape.
• Correct custom and automatic drop classification for containers and derived types.
• Preserve payload mutability in derived enums and classify custom niches as NonRobust.
• Check unresolved enum discriminants against the inferred tag range.