fix(dashboard): use learner view for lesson lock empty states (#764)

Lock checks gated on isOrgStudent missed org-site students where
isStudentExperience is true but org role may be unset. Introduce
isCourseLearnerView (student experience OR org student) and mirror
the exercise page branch structure so locked lessons always show
StudentContentLockedNotice instead of the teacher empty state.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

apps/dashboard/src/lib/utils/store/app.ts

@@ -32,6 +32,19 @@ export const isStudentExperience = derived([globalStore, isOrgStudent], ([$gs, $
   return $isStudent ?? false;
 });
 
+/**
+ * True when course lesson/exercise pages should render the learner UI
+ * (locked notices, student empty states, no teacher authoring CTAs).
+ * Cloud org-site visitors always get the learner view; on the app host
+ * only org-role students do.
+ */
+export const isCourseLearnerView = derived(
+  [isStudentExperience, isOrgStudent],
+  ([$isStudentExperience, $isOrgStudent]) => {
+    return $isStudentExperience || $isOrgStudent === true;
+  }
+);
+
 /**
  * The root path for navigation: '/lms' for students, '/org/{siteName}' for admin/teacher
  */