Extract reverse-lookup scan to core/relationships (one shared impl)

src/app/components/DatasetsModal.tsx

@@ -16,6 +16,7 @@ import { useState } from 'react';
 import { useShallow } from 'zustand/react/shallow';
 import { datasetReference, type DataSource, type Dataset } from '@core/dataset';
 import { detectFormat, detectFormatFromUrl, type DataFormat } from '@core/format-detection';
+import { datasetUsageCounts, snippetsReferencingDataset } from '@core/relationships';
 import { closeModal, openModal, resnapshot } from '../modals/ModalCoordinator';
 import { confirm } from '../stores/ConfirmStore';
 import { notify } from '../stores/NotificationStore';
@@ -44,18 +45,6 @@ function humanBytes(bytes: number): string {
   return `${mb < 10 ? mb.toFixed(1) : Math.round(mb)} MB`;
 }
 
-/** Map of dataset name (lower-cased) → how many snippets reference it. */
-function usageByName(snippets: ReadonlyArray<{ datasetRefs: string[] }>): Map<string, number> {
-  const counts = new Map<string, number>();
-  for (const s of snippets) {
-    for (const ref of s.datasetRefs) {
-      const key = ref.toLowerCase();
-      counts.set(key, (counts.get(key) ?? 0) + 1);
-    }
-  }
-  return counts;
-}
-
 const SOURCE_OPTIONS: ReadonlyArray<SegmentedOption<DataSource>> = [
   { value: 'inline', label: 'Inline' },
   { value: 'url', label: 'URL' },
@@ -70,7 +59,7 @@ export function DatasetsModal() {
   const select = useDatasetStore((s) => s.select);
   const startCreate = useDatasetStore((s) => s.startCreate);
 
-  const usage = usageByName(snippets);
+  const usage = datasetUsageCounts(snippets);
   const ordered = [...datasets].sort(byModifiedDesc);
 
   const handleNew = () => {
@@ -165,8 +154,7 @@ function DatasetDetail({
   const selectSnippet = useSnippetStore((s) => s.selectSnippet);
   const [copied, setCopied] = useState(false);
 
-  const lower = dataset.name.toLowerCase();
-  const linked = snippets.filter((s) => s.datasetRefs.some((r) => r.toLowerCase() === lower));
+  const linked = snippetsReferencingDataset(snippets, dataset.name);
 
   const handleEdit = () => {
     startEdit();