Gate advanced course enrollment on assessment / skillLevel

[jeromehardaway]

Problem

The assessment (/assessment) records a skillLevel on the user, but nothing in the enrollment flow consults it. Students can enroll in advanced courses (e.g., Advanced AI Engineering) with no prerequisite check.

Expected behavior

Courses declared as ADVANCED difficulty require the enrolling user to have a minimum recorded skillLevel (or a documented instructor override).

Acceptance criteria

• Enrollment API (/api/enrollments or equivalent) rejects enrollment in ADVANCED courses for users below the threshold.
• Client-side UI disables/explains the block (don't let the user submit and then fail).
• Instructor/admin override path exists.
• Tests cover the gating logic.

Blocked by

• Assessment does not actually run user code — skill levels recorded are invalid #1056 (assessment must actually work before its output can gate anything).

Suggested approach

Server-side check in enrollment handler:

if (course.difficulty === "ADVANCED" && user.skillLevel !== "SENIOR") {
  return res.status(403).json({ error: "Prerequisite: complete the skill assessment." });
}