feat(short): el ejemplo del prompt habla, y por eso los specs vuelven a hablar

La primera generación con narración viva narró 5 de 7 planos. La siguiente, ya
con la sección de presupuestos de ancho en el prompt, narró 1 de 8.

La causa no era la sección 3b sino la 5: el ejemplo trabajado — un spec completo
de 8 planos presentado como "el que produjo un buen vídeo" — no llevaba ni una
narración, porque es anterior a la voz. Contra esa señal de formato, una regla
en prosa que además dice "no todos los planos necesitan una" pierde siempre.

Ahora el ejemplo narra 6 de sus 8 y calla en los dos que dibujan una cita, donde
la voz sólo competiría con palabras que ya están en pantalla. Sus duraciones
suben para pagar lo que habla: un plano que se queda corto para su propia voz
enseñaría a infradeclarar, y el render no corta la voz, alarga el plano. La
ventana de silencio se recoloca porque seguía a document_quote por tiempo.

El aviso de ancho ya no cita el hueco de 16 caracteres de quote_a: shortsmith
envuelve esas citas en dos líneas y el presupuesto vivo es 31.

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

src/generator/shortspec.py

@@ -92,10 +92,10 @@ a card with four rows needs longer than a headline.
 SHORT, UPPERCASE, no trailing punctuation. A headline is 2-5 words.
 - **"CABE ~N caracteres dibujados" is a width, and it is the one limit nothing \
 will catch for you.** Nothing rejects a longer string: the renderer shrinks the \
-type until it fits, so a quote of 58 characters in a 16-character slot is drawn \
-at a quarter of its size and ends up the smallest text on a frame it was \
-supposed to dominate. Stay at or under N. On a quote that means picking a \
-shorter verbatim span, never squeezing the whole sentence in.
+type until it fits, so a string at twice its budget is drawn at a fraction of \
+its size and ends up the smallest text on a frame it was supposed to dominate. \
+Stay at or under N. On a quote that means picking a shorter verbatim span, \
+never squeezing the whole sentence in.
 - Respect every max length and list-length limit above. They are enforced.
 - Colours are palette names ({colors}) — never hex.
 - Quotes carry the typographic quote marks: “SPLIT RADAR IMAGE”, with U+201C \
@@ -127,8 +127,15 @@ punctuation, whole words. The on-screen props are terse and uppercase; the \
 narration is a person talking. Write "seventeenth of November" rather than \
 "17 NOV" — the voice reads exactly what you type, and it will say "one seven \
 N-O-V" if you make it.
-- Not every shot needs one. Silence over a single strong image is a choice, \
-and a wall of continuous talking is not.
+- **Most shots carry one.** The example narrates six of its eight and leaves \
+silent exactly the two that draw a quotation, where the voice would only be \
+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.
+- Narration costs seconds. A shot is never cut short to fit the voice — it \
+grows instead — so a line that needs six seconds in a four-second shot pushes \
+your whole total past the target. Write the line, then give the shot the time \
+the line actually takes.
 - Everything in section 4 applies to narration word for word. It is prose you \
 compose rather than a label you copy, which makes it the easiest place to \
 slip in a figure no source gave you — and it is checked exactly like the rest.
@@ -155,7 +162,8 @@ state the fact plainly.
 # 5. A worked example — FORMAT ONLY
 
 This is a case_file that produced a good video. Read it for shape: how long a \
-shot runs, how a headline is worded, how the shots build.
+shot runs, how a headline is worded, which shots speak and which stay silent, \
+how the shots build.
 
 It is not source material. Do not reuse its strings, figures, coordinates, \
 quotes or waypoints — not even if it covers the same case you were asked \