1A: refined clip timings (cue trimming, gap compression), 512px recomposed images, four Figure-8 panels, activity-wide Figure-5 map; SHOW_PROMPT migration + INTRO fixes for remaining lessons

Co-authored-by: Cursor <cursoragent@cursor.com>

lesson-4B.module

@@ -108,7 +108,6 @@ $LESSON Figure 4
 
 $SELECT Choose the best answer
 INSTRUCTION: Listen to the question and tap the best answer.
-AUDIO_ONLY
 OPTION: a | Yes, I can buy two tapes.
 OPTION: b | No, I don't work here.
 OPTION: c | Yes, it does. It sells recorders, too.
@@ -144,7 +143,6 @@ $LESSON Figure 5
 
 $SELECT Listen and Choose A or B
 INSTRUCTION: Listen to the situation and tap the correct answer.
-AUDIO_ONLY
 
 PROMPT: Henry wanted to listen to music. His friends didn't want to hear it. What did Henry put on? {bk04-l4b-f5-01.mp3}
 OPTION: a | his headset