REALM-005: Copy-type auto-escape (no promote needed for primitives)

[Raulgooo]

Summary

Primitive types and value structs (copy types) should be returnable from inner scopes without promote(). The realm checker must not produce false positive errors for them.

Acceptance Criteria

• i32 x = stack_fn() where stack_fn is stack-realm → no realm escape error
• Pointer return from inner scope without promote → realm escape error (correct)
• All primitive types (i8, i16, i32, i64, u8, u16, u32, u64, f32, f64, bool, char) treated as copy types

Depends on

• REALM-001, REALM-002

Related

• Spec §8