vocab: stop re-teaching a word later in the same session (239 tags)

A word tagged VOCAB in one activity was tagged again in later activities of the
same session, so the learner got the same chip repeatedly — most visibly in the
pronunciation drills, which re-listed every word from the dialogue before them
(reported: book 7 session 1-2). Rule applied: drop a VOCAB whose word was
already tagged in an EARLIER activity of that session. Repeats INSIDE one
activity are kept — those teach distinct senses ('stuck to his finger' vs
'stuck the milk in the fridge', 'shop' as verb then noun). Also dropped chips
for plurals of already-known words in book 7 session 1-2, where the drill
teaches the singular/plural pair rather than new vocabulary. No session lost
all of its vocabulary (verified).

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

book-7-lesson-2.module

@@ -267,13 +267,10 @@ INTRO: Here's what those circle words actually mean. Listen and repeat each defi
 INSTRUCTION: Listen and repeat the sentences.
 REPEAT
 
-VOCAB: circumference
 LINE: The line on the outside of a circle is called the circumference.
 
-VOCAB: diameter
 LINE: The line from one side of a circle to the other side is the diameter. It touches the center of the circle.
 
-VOCAB: radius
 LINE: We call the line from the outside of a circle to the center of the circle the radius.
 
 VOCAB: half
@@ -781,7 +778,6 @@ LINE: Multiply. We learned to multiply in class today. {bk07-l2b-f5-04.mp3}
 VOCAB: subtract
 LINE: Subtract. I must learn to subtract. {bk07-l2b-f5-05.mp3}
 
-VOCAB: understand
 LINE: Understand. Do you understand this math? {page_047_001.jpg} {bk07-l2b-f5-06.mp3}
 
 VOCAB: minus
@@ -793,7 +789,6 @@ LINE: Plus. 1 plus 1 equals 2. {bk07-l2b-f5-08.mp3}
 VOCAB: times
 LINE: Times. 2 times 5 equals 10. {bk07-l2b-f5-09.mp3}
 
-VOCAB: problem
 LINE: Problem. This is a hard math problem. {bk07-l2b-f5-10.mp3}
 
 VOCAB: half
@@ -1237,7 +1232,6 @@ INTRO: How to talk prices in a store: so much a pound, three for a dollar. Liste
 INSTRUCTION: Listen and repeat the words and sentences.
 REPEAT
 
-VOCAB: price
 LINE: The price of each apple is 20 cents. Each apple costs 20 cents.
 
 LINE: What's the price of bananas? Bananas are 35 cents a pound today.