fix(short): el divisor del prompt iba redondeado y no reproducía su propia cuenta

12 ÷ 2.8 no da 5.1, da 5.0. La cuenta trabajada la hace el modelo con el número
que ve, así que el número que ve tiene que ser el real.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/generator/shortspec.py

@@ -183,11 +183,11 @@ competing with words already on the frame. Chosen silence is an edit; a spec \
 with one narrated shot out of eight is not a Short with a voice, it is a Short \
 that forgot to speak.
 - **Give every narrated shot enough time for its own line, and work it out \
-rather than guessing.** The voice reads about {words_per_second:.1f} words a \
+rather than guessing.** The voice reads about {words_per_second:g} words a \
 second and pauses a quarter second at every full stop, so **count the words AND \
 count the sentences**:
 
-      duration ≥ words ÷ {words_per_second:.1f} + {sentence_pause} × sentences + \
+      duration ≥ words ÷ {words_per_second:g} + {sentence_pause} × sentences + \
 {rounded_pad}
 
   The second term is the one that catches people out. "Witness identities. \
@@ -196,9 +196,9 @@ not a fast line, it is three quarters of a second of silence on top. Two lines \
 of the same length do not take the same time if one of them is chopped.
 
   Worked, on the example below: shot 1 speaks twelve words in one sentence, so \
-12 ÷ {words_per_second:.1f} + {sentence_pause} + {rounded_pad} = 5.1, and it \
+12 ÷ {words_per_second:g} + {sentence_pause} + {rounded_pad} = 5.1, and it \
 declares 5.5. Shot 4 speaks thirteen words in two sentences, so 13 ÷ \
-{words_per_second:.1f} + 0.5 + {rounded_pad} = 5.7, and it declares 6.0. Round \
+{words_per_second:g} + 0.5 + {rounded_pad} = 5.7, and it declares 6.0. Round \
 up, never down.
 
   This is the one rule that makes your own arithmetic true: a shot runs for the LONGER of \