Type ascription produces two incompatible fields (#7355)

# Symptoms

This code produces a big ugly confusing error in the frontend, see #7340.

# Root cause

I added a new test case, with an unknown type. In `ast.snap` under `body[0].declaration.init.ty` there two different `type` fields in the AST node for the type's name, and they have conflicting values Primitive and Identifier.

<img width="602" alt="Screenshot 2025-06-03 at 4 04 55 PM" src="https://github.com/user-attachments/assets/913a0fa0-3e8d-473f-bb64-003d44915be0" />

# Solution

Change the `enum PrimitiveType` variant from `Named(Node<Identifier>)` to `Named { name: Node<Identifier> }` so that the fields nest differently.

Now the error correctly points out to the user that the type `NotARealType` can't be found. Much better error message that shows the user the problem.

# Alternative solutions

Stop the duplicated JSON fields altogether. I tried this previously in https://github.com/KittyCAD/modeling-app/pull/4369 but it was very involved, and I didn't think it was worth it. Maybe I should reopen that PR and solve this properly.

Closes #7340

rust/kcl-lib/src/execution/types.rs

@@ -187,7 +187,7 @@ impl RuntimeType {
                 };
                 RuntimeType::Primitive(PrimitiveType::Number(ty))
             }
-            AstPrimitiveType::Named(name) => Self::from_alias(&name.name, exec_state, source_range)?,
+            AstPrimitiveType::Named { id } => Self::from_alias(&id.name, exec_state, source_range)?,
             AstPrimitiveType::Tag => RuntimeType::Primitive(PrimitiveType::Tag),
             AstPrimitiveType::ImportedGeometry => RuntimeType::Primitive(PrimitiveType::ImportedGeometry),
             AstPrimitiveType::Function(_) => RuntimeType::Primitive(PrimitiveType::Function),