Component docs: link to the rerun datatype the component wraps (#7996)

### What
* Follow-up to #7986

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7996?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7996?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/7996)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

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crates/build/re_types_builder/src/codegen/docs/mod.rs

@@ -476,8 +476,16 @@ fn write_fields(objects: &Objects, o: &mut String, object: &Object) {
     }
 
     if object.is_arrow_transparent() {
-        debug_assert!(object.is_struct());
-        debug_assert_eq!(object.fields.len(), 1);
+        assert!(object.is_struct());
+        assert_eq!(object.fields.len(), 1);
+        let field_type = &object.fields[0].typ;
+        if object.kind == ObjectKind::Component && matches!(field_type, Type::Object(_)) {
+            putln!(o, "## Rerun datatype");
+            putln!(o, "{}", type_info(objects, field_type));
+            putln!(o);
+        } else {
+            // The arrow datatype section covers it
+        }
         return; // This is just a wrapper type, so don't show the "Fields" section
     }