Proposition Summary Dto
data class PropositionSummaryDto(val id: String, val text: String, val confidence: Double, val status: String, val mentions: List<EntityMentionSummaryDto>, val grounding: List<String>)
A lean proposition summary — the common shape every discovery result maps down to.
Grounding is carried as opaque string chunk ids only; no RAG or store types cross this boundary.