Add OpenAudio emotion/tone cues to generated scripts

Instruct the scriptwriter to add inline parenthetical cues from OpenAudio
S1's supported set — (excited) (chuckling) (laughing) (sighing) (whispering)
etc. — sparingly where they fit. These pass through parse_script and the TTS
request unchanged, so the model renders them as emotion/tone.

Note: S1 uses parentheses, not square brackets, and has no pause/emphasis
marker (punctuation handles those), so the prompt steers away from [chuckle]
-style tags that would otherwise be read aloud.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

research/graph.py

@@ -96,9 +96,18 @@ def write_node(state: ResearchState) -> dict:
             f"Speakers: {speaker_list}.\n"
             "Format STRICTLY as one line per turn, prefixed with the speaker name and a "
             f"colon, like:\n{fmt}\n"
-            "Do not include stage directions, markdown, or headings - only spoken dialogue "
-            "lines. Keep each line to a few sentences. Open with a hook and close with a "
-            "sign-off."
+            "Make the delivery feel human by adding OpenAudio emotion/tone cues IN "
+            "PARENTHESES, inline, right before the words they color (or at the very start "
+            "of a turn). Use ONLY these cues: (excited) (curious) (surprised) (amused) "
+            "(interested) (confident) (empathetic) (joyful) (serious) (sarcastic) "
+            "(thoughtful) (laughing) (chuckling) (sighing) (whispering) (soft tone) "
+            "(in a hurry tone). Use them sparingly — about one every few lines, only where "
+            "it genuinely fits the moment. Do NOT invent other cues and do NOT use square "
+            "brackets. There is no pause or emphasis marker: convey pauses and emphasis with "
+            "natural punctuation (commas, em-dashes —, ellipses …).\n"
+            "Apart from these inline parenthetical cues, output only spoken dialogue — no "
+            "markdown, headings, or stand-alone stage directions. Keep each line to a few "
+            "sentences. Open with a hook and close with a sign-off."
         ),
         user=(
             f"Topic: {state['topic']}\n"