Discuss support for narrowing

Sharing corridor discussion with @RyanJK5:

```
struct A {
void a();
};

struct B {
void b();
};

struct C {
void c();
};

struct D: A, B, C {};

protocol p;

protocol_view vp(p);
```

No file, test, or entry point is identified. Start by reviewing the protocol and protocol_view usage shown in the example, then clarify the intended narrowing behavior and acceptance criteria before locating the implementation and tests.

Written by the indexing model from the issue text.