Add custom intervention modals

lib/create/mergePresetMethodsWithCustom.ts

@@ -0,0 +1,32 @@
+/**
+ * Merge JSON preset method rows with user-created cards (stable UUID ids + meta).
+ * Custom rows follow `selectedIds` order (most-recent add at index 0 in create flow)
+ * but appear after all presets in this merged list; CardStack display order is
+ * layered separately via `useMethodCardDeckOrdering`.
+ */
+
+export function mergePresetMethodsWithCustom<
+  T extends { id: string; label: string; supportText?: string },
+>(
+  presets: readonly T[],
+  selectedIds: readonly string[],
+  meta: Record<string, { label: string; supportText: string }> | undefined,
+): T[] {
+  const presetIds = new Set(presets.map((p) => p.id));
+  const customRows: T[] = [];
+  const seenCustom = new Set<string>();
+
+  for (const id of selectedIds) {
+    if (presetIds.has(id)) continue;
+    const row = meta?.[id];
+    if (!row || seenCustom.has(id)) continue;
+    seenCustom.add(id);
+    customRows.push({
+      id,
+      label: row.label,
+      supportText: row.supportText,
+    } as T);
+  }
+
+  return [...presets, ...customRows];
+}