Close section drawer on save and enable activities for activity sections

[nicpottier]

Summary

• Close section drawer panel immediately on save while waiting for re-render
• Fix activities feature flag to detect activity section types (e.g., activity_multiple_choice, activity_matching) in addition to quiz pages
• The packaging code was only checking for quiz-generation quizzes, missing activity sections from page-sectioning data

Test plan

• Re-open the section editor, make changes, and save — verify drawer closes immediately
• Generate a book with activity sections and open the preview — verify the submit button appears on activity sections
• Test with both activity sections and quiz pages to ensure both are detected