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-8-lesson-3.module

@@ -165,7 +165,6 @@ LINE: The call just cost a quarter. {bk08-l3a-f2-03.mp3}
 VOCAB: local
 LINE: Local calls are calls inside a city. {bk08-l3a-f2-04.mp3}
 
-VOCAB: change
 LINE: Coins are called change. {bk08-l3a-f2-05.mp3}
 
 VOCAB: operator
@@ -180,7 +179,6 @@ LINE: A public phone usually costs money. {bk08-l3a-f2-08.mp3}
 VOCAB: person
 LINE: He is the person I was calling. {bk08-l3a-f2-09.mp3}
 
-VOCAB: slot
 LINE: Put the money in the slot. {bk08-l3a-f2-10.mp3}
 
 # Source: LLA 3A Figure 3
@@ -217,19 +215,15 @@ REPEAT
 VOCAB: page
 LINE: The phone book has many pages. There are maps of the city at the back of the phone book. {st-page_099_001.jpg}
 
-VOCAB: person
 LINE: How many people are there in the room? There is only one person in the room. {st-page_099_002.jpg}
 
-VOCAB: just
 LINE: Do you have any money? I have just two dollars. Or, I just have two dollars. {st-page_099_003.jpg}
 
 VOCAB: to find | found
 LINE: What did you find? I found a coin. {st-page_099_004.jpg}
 
-VOCAB: expensive
 LINE: This radio costs $195.00. It's expensive. {st-page_100_001.jpg}
 
-VOCAB: cheap
 LINE: The other radio costs $15.00. It's cheap. {st-page_100_002.jpg}
 
 # Source: ST §Word Bank (The Book Was Expensive)