Migrate NPC normalization to shared reconciliation

internal/modules/dnd/normalize/npcs/assets/prompts/task.md

@@ -1,2 +1,8 @@
-Identify only supplied NPC display names that clearly refer to the same
-individual in the supplied transcript context.
+Review NPC candidates and their cited transcript context to identify aliases
+that refer to the same individual. Propose only groups supported by the
+transcript, and preserve distinct individuals even when their names are
+similar.
+
+For every accepted group, choose as canonical the supplied candidate whose
+display name is the most complete and clear NPC name. Do not invent, edit, or
+combine display names.