Simplify D&D scene chunking responses

internal/modules/dnd/chunk/scenes/assets/prompts/task.md

@@ -1,5 +1,18 @@
 Divide the provided transcript into coherent Dungeons & Dragons scenes for the
-dnd/scenes chunk module.
+`dnd/scenes` chunk module.
 
-A scene is a coherent unit of play. Start a new scene when there is a meaningful
-change in location, objective, threat, activity, encounter, or mode of play.
+A scene is a coherent unit of play. Start a new scene when the transcript
+establishes a meaningful change in location, objective, threat, activity,
+encounter, or mode of play. Good reasons include a material move, beginning or
+ending combat, a substantially different encounter phase, a shift between
+combat, exploration, social interaction, planning, travel, rest, or downtime,
+a change in the central NPC, faction, threat, or objective, or a sustained
+table-level interruption that materially changes the activity.
+
+Do not split a scene merely because a speaker or combat round changes, a
+routine turn occurs, or the table briefly digresses. Prefer fewer coherent
+scenes over speculative or fine-grained boundaries.
+
+Return only inclusive `start_unit_id` and `end_unit_id` endpoints for each
+scene. Do not return titles, modes, participants, summaries, boundary notes,
+confidence, caveats, final chunk IDs, or chunk indexes.