stable session ids: prefix the 3 unprefixed $LESSON titles (book-11 dup 'Dialogues and Comprehension' collided across files and broke the manifest join); repair book-11-lesson-1 session headers polluted by the earlier activity rebuild (source-file $LESSON lines had leaked in)

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

book-11-lesson-1.module

@@ -1118,7 +1118,7 @@ ANSWER: f
 FEEDBACK: Side 4 is 3 inches long. {bk11-l1c-f2-01p.mp3}
 
 
-$LESSON The Present Perfect Tense
+$LESSON 1-7: The Present Perfect
 
 # Source: ST §The Present Perfect Tense
 
@@ -1352,7 +1352,6 @@ PROMPT: Has he been home since Thursday evening? {bk11-l1c-f7-01k.mp3}
 RESPONSE: Yes, he's been home since 6:45 Thursday evening. {bk11-l1c-f7-01l.mp3}
 
 
-$LESSON How Long?
 
 # Source: ST §Answer with the Present Perfect
 
@@ -1544,7 +1543,6 @@ PROMPT: Doug has a problem with math. {bk11-l1c-f9-01q.mp3}
 RESPONSE: How long has he had a problem with math? {bk11-l1c-f9-01r.mp3}
 
 
-$LESSON Listening Skills
 
 # Source: ST §How Long Will You Be There?
 

book-11-lesson-3.module

@@ -157,7 +157,7 @@ ANSWER: i
 FEEDBACK: The mechanic gave me a 90-day guarantee. {bk11-l3a-f1-p30.mp3}
 
 
-$LESSON Dialogues and Comprehension
+$LESSON 3-1b: Dialogues and Comprehension (1)
 
 # Source: LLA 3A Figure 1 (Part 2), second half of the split pool
 
@@ -230,7 +230,7 @@ ANSWER: i
 FEEDBACK: The mechanic gave me a 90-day guarantee. {bk11-l3a-f1-p30.mp3}
 
 
-$LESSON Dialogues and Comprehension
+$LESSON 3-1c: Dialogues and Comprehension (2)
 
 # Source: ST §What's That Noise?
 

book-12-lesson-3.module

@@ -932,7 +932,7 @@ PROMPT: Who has been in the major's office for the last hour? {bk12-l3d-f9-21.mp
 RESPONSE: It could be Lieutenant Mitchell. {bk12-l3d-f9-22.mp3}
 
 
-$LESSON Present Perfect Tense
+$LESSON 3-3b: Present Perfect Tense
 
 # Source: ST §I'm Not Sure. It Could Be...