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-4.module

@@ -118,7 +118,6 @@ Mr_Brown: Yes. Please tell him Ed Brown called. I'll call him back at home tonig
 Mr_Miller: I'm back! Did I get any calls? {st-page_127_004.jpg}
 Ms_Craft: Yes, Mr. Brown called.
 
-VOCAB: leave a message
 Mr_Miller: Did he leave a message?
 Ms_Craft: It's on your desk.
 Mr_Miller: Thank you, Ms. Craft.
@@ -1178,21 +1177,16 @@ LINE: Last Sunday, Lt West looked for an apartment. {st-page_150_001.jpg}
 LINE: She needs to find one before the last day of the month.
 LINE: She drove on Vail Street, and she saw a nice apartment building.
 
-VOCAB: for rent
 LINE: There were some apartments for rent.
 
-VOCAB: manager
 LINE: She went to the office and talked to the manager. {st-page_150_002.jpg}
 
-VOCAB: bedroom
 VOCAB: dining room
 LINE: The manager showed her a two-bedroom apartment. It was nice.
 LINE: The kitchen was small, but the bedrooms and the living room were big.
 
-VOCAB: rent
 LINE: "The rent is $450.00 a month," the manager said.
 
-VOCAB: deposit
 LINE: He also told her about a deposit.
 LINE: "What kind of deposit?" She asked him.