Copying a struct with a bool produces invalid select statement

https://godbolt.org/z/srbW3T8Tc

```glsl
#version 460
#extension GL_EXT_shader_explicit_arithmetic_types_int64 : require
#extension GL_EXT_buffer_reference2 : require

struct S1 { bool x; };

layout(set = 0, binding = 1) restrict readonly buffer SSBO {
S1 s1;
} InBuffer;

layout(buffer_reference) buffer MyBuffer {
S1 s1;
};

void main() {
MyBuffer payload;
payload.s1 = InBuffer.s1;
}
```

generates invalid SPIR-V

```
Expected bool scalar or vector type as condition: Select
%29 = OpSelect %uint %28 %uint_1 %uint_0
```

Start with the Godbolt reproducer in the issue and inspect the generated SPIR-V around the reported OpSelect diagnostic. Done means the struct-copy example no longer generates invalid SPIR-V with a non-boolean select condition.

Written by the indexing model from the issue text.