Standardize D&D prompt asset filenames

assets/dnd/location-occurrences/prompts/location-registry.md

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+A normalized location registry is provided below for identity grounding. It may
+be empty. Each record contains the exact location ID and canonical display name
+to copy when the transcript establishes an occurrence of that place.
+
+Registry content is context, not occurrence evidence. Do not derive an
+occurrence or a source range from the registry, and do not infer a location
+that is absent from it.
+
+{{ input "locations" }}