Function
The lesson to check
true once the learner's state reports the lesson complete
Reads through the shared learner store rather than per-component state, so every surface showing completion agrees: a lesson marked while the outline and a video row are both mounted updates both, with no reload.
Marks appear only after hydration. That is why the indicator must express completed and never "not completed" — the pre-hydration frame omits information rather than asserting something false about the learner's progress.
Browser-side only — do NOT call from a Server Component.
Whether the signed-in learner has completed a lesson.