`for i in 0..1 { let x: u32 = i+1; }` compiles successfully but generates invalid wgsl

if you write:
```rust
#[wgsl]
pub my_shader{
// ...
for i in 0..1{
let x: u32 = i+1;
}
// ...
}
```
it compiles successfully, but when you try to run the wgsl shader:
```
Shader validation error: Entry point compute at Compute is invalid
┌─ compute:839:21
│
839 │ let x:u32 = i+1;
│ ^^^^ naga::ir::Expression [40]
│
= Expression [40] is invalid
= Operation Add can't work with [20] (of type Scalar(Scalar { kind: Uint, width: 4 })) and [39] (of type Scalar(Scalar { kind: Sint, width: 4 }))
```

If you try
```rust
#[wgsl]
pub my_shader{
// ...
for i in 0..1u32{
let x: u32 = i+1;
}
// ...
}
```
The generated wgsl loop var and the condition have different types:
```
Shader validation error: Entry point compute at Compute is invalid
┌─ compute:838:21
│
838 │ for (var i = 0; i < 1u; i++) {
│ ^^^^^^ naga::ir::Expression [37]
│
= Expression [37] is invalid
```

To get it to work you have to write:
```rust
#[wgsl]
pub my_shader{
// ...
for i in 0u32..1u32{
let x: u32 = i+1;
}
// ...
}
```

Start with the #[wgsl] loop expansion that produces the generated WGSL shown in the report, and trace how range bounds and the loop variable types are inferred. Reproduce both failing examples, then verify that generated loops using u32 bounds validate successfully without requiring redundant casts.

Written by the indexing model from the issue text.