Add fast-follows to the AI onboarding flow (#34737)

Follow-up to https://github.com/zed-industries/zed/pull/33738.

Release Notes:

- N/A

---------

Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>

crates/language_model/src/registry.rs

@@ -206,8 +206,8 @@ impl LanguageModelRegistry {
         None
     }
 
-    /// Check that we have at least one provider that is authenticated.
-    fn has_authenticated_provider(&self, cx: &App) -> bool {
+    /// Returns `true` if at least one provider that is authenticated.
+    pub fn has_authenticated_provider(&self, cx: &App) -> bool {
         self.providers.values().any(|p| p.is_authenticated(cx))
     }