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-9-lesson-2.module

@@ -156,11 +156,9 @@ INTRO: More words for life on the road — bicycles, curves, heavy traffic, and
 INSTRUCTION: Look at the pictures and repeat the sentences.
 REPEAT
 
-VOCAB: automobile
 VOCAB: auto
 LINE: The automobile on the left side of the road is white. The auto on the right side is black. {st-page_047_001.jpg}
 
-VOCAB: accident
 LINE: The drivers of the autos had an accident. It happened on the corner of 4th and Elm. {st-page_047_002.jpg}
 
 VOCAB: bicycle
@@ -176,11 +174,9 @@ VOCAB: careful
 VOCAB: to cross | cross
 LINE: Be careful! Don't cross the street when a bus is coming. {st-page_048_002.jpg}
 
-VOCAB: policeman
 LINE: Jim's father is a policeman. His car has red and blue lights on top. {st-page_048_003.jpg}
 
 VOCAB: curve
-VOCAB: careless
 LINE: This driver is going very fast around the curve. He's a careless driver. {st-page_048_004.jpg}
 
 VOCAB: traffic
@@ -286,7 +282,6 @@ INSTRUCTION: Repeat the key phrases and read the sentences.
 REPEAT
 
 VOCAB: bicycle rider
-VOCAB: careless
 LINE: The bicycle rider was careless. He didn't stop when the light turned red.
 
 VOCAB: ran the red light
@@ -298,7 +293,6 @@ LINE: The driver of the car had to make a fast stop.
 VOCAB: ran into the light pole
 LINE: He ran into the light pole.
 
-VOCAB: caused the accident
 VOCAB: He was at fault
 LINE: The bicycle rider caused the accident. He was at fault.
 
@@ -533,11 +527,9 @@ VOCAB: cross
 LINE: Don't cross the street when the sign says DON'T WALK. {st-page_062_001.jpg}
 
 VOCAB: keep to the right side
-VOCAB: law
 LINE: In the U.S., you must keep to the right side of the street. It's the law. {st-page_062_002.jpg}
 
 VOCAB: seat belts
-VOCAB: obey
 LINE: In Texas, all drivers must wear their seat belts. Mrs. Adams and her son obey the law. {st-page_062_003.jpg}
 
 VOCAB: fastens