Add missing comment annotation

Author: soareschen

content/blog/2025-10-12-v0.5.0-release.md

@@ -205,9 +205,9 @@ Unlike the original typestate builder, the type of the builder remains `__Partia
 You can also use the optional builder with `finalize_with_default` if all fields in the extensible record implement `Default`. In that case, you can safely finalize the record without handling a potential error:
 
 ```rust
-let foo_bar = FooBar::optional_builder()
-    .set(PhantomData::<Symbol!("foo")>, "foo".to_owned())
-    .finalize_with_default();
+let foo_bar = FooBar::optional_builder() // __PartialFooBar<IsOptional, IsOptional>
+    .set(PhantomData::<Symbol!("foo")>, "foo".to_owned()) // __PartialFooBar<IsOptional, IsOptional>
+    .finalize_with_default(); // FooBar
 ```
 
 The optional builder is used by [`cgp-serde`](https://github.com/contextgeneric/cgp-serde/blob/46ff47fce3aa3e57700340a05833b404b9d59ddf/crates/cgp-serde/src/providers/record.rs#L49-L65) to implement generic deserialization for extensible records.