fix(web): styled role-filtered nav, hidden on phones; clearer studio preview label

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/feature-studio/src/ui/learnerPreview.tsx

@@ -16,7 +16,7 @@ export default function LearnerLessonPreview(props: LessonPreviewProps) {
     return {
       courseId, courseTitle: "",
       lesson: { id: lesson?.id ?? "preview", title: lesson?.title ?? "", type: lesson?.type === "exercise" ? "exercise" : "text", minutes: null },
-      module: { id: "", title: "Preview", index: 0 },
+      module: { id: "", title: "Draft, not published", index: 0 },
       locked: false,
       markdown: body, baseFile: resolveCourseUrl ? file ?? null : null, trackMarkdown: {}, tracks: [],
       video: null, transcript: null, hints: [], decks: [], code: null, attachments: [], browser: null, localCommand: null,