Update doc comments

crates/fj/src/models/context.rs

@@ -1,7 +1,5 @@
 /// Contextual information passed to a [`Model`][crate::models::Model] when it
 /// is being initialized.
-///
-/// Check out the [`ContextExt`] trait for some helper methods.
 pub trait Context {
     /// Get an argument that was passed to this model.
     fn get_argument(&self, name: &str) -> Option<&str>;

crates/fj/src/models/host.rs

@@ -11,6 +11,8 @@ pub trait Host {
 }
 
 /// Extension methods to augment the [`Host`] API.
+///
+/// The purpose of this trait is to keep [`Host`] object-safe.
 pub trait HostExt {
     /// Register a model with the Fornjot runtime.
     fn register_model<M>(&mut self, model: M)