using VecN<bool> causes invalid WGSL

vec2b, vec3b, vec4b aren't builtin aliases in the [WGSL spec](https://www.w3.org/TR/2026/CRD-WGSL-20260831/#vector-types)

```
#[wgsl]
pub mod my_shader {
#[compute]
#[workgroup_size(1, 1, 1)]
pub fn compute() {
let x: Vec2b = vec2b(false, false);
}
}
```

compiles successfully, but if you try to run the generated WGSL:

```
Shader 'my_shader' parsing error: no definition in scope for identifier: `vec2b`
┌─ wgsl:66:12
│
66 │ let x: vec2b = vec2(false, false);
│ ^^^^^ unknown identifier
```

I think the easiest fix is just to add [custom aliases](https://www.w3.org/TR/2026/CRD-WGSL-20260831/#type-aliases) into the generated WGSL, e.g. `alias vec2b = Vec2;`

Start by reproducing the provided #[wgsl] shader and inspecting its generated WGSL, especially the Vec2b type and vec2b constructor. Add the required boolean-vector aliases to the generated output, then verify that the output parses and no longer reports vec2b as an unknown identifier.

Written by the indexing model from the issue text.