feat: add @TypeOf type hints for compiled templates

- Add TypeHint node type in parser for //- @TypeOf(field): type syntax
- Support scalar types (f32, i32, bool, etc.) and array/struct types
- Use helpers.appendValue() for non-string typed fields
- Filter out loop variable references from Data struct fields
- Preserve @TypeOf comments during comment stripping

Example usage:
  //- @TypeOf(subtotal): f32
  span $#{subtotal}

  //- @TypeOf(items): []{name: []const u8, price: f32}
  each item in items
    h3 #{item.name}

src/walk.zig

@@ -351,6 +351,7 @@ fn visitChildren(
         .MixinBlock,
         .YieldBlock,
         .Text,
+        .TypeHint,
         => {},
     }
 }