feat: add token breakdown helpers

lib/token-breakdown.ts

@@ -0,0 +1,35 @@
+import { sortDetailBreakdown, type DetailBreakdownItem, type DetailBreakdownSortKey } from "./detail-sort";
+
+export interface TokenBreakdownItem extends DetailBreakdownItem {
+  models: DetailBreakdownItem[];
+}
+
+export type TokenBreakdownSortKey = DetailBreakdownSortKey;
+
+export function sortTokenBreakdown(
+  items: TokenBreakdownItem[],
+  sortKey: TokenBreakdownSortKey,
+  sortAsc: boolean
+): TokenBreakdownItem[] {
+  return sortDetailBreakdown(items, sortKey, sortAsc);
+}
+
+export function getTokenDisplayName(name: string, unnamedLabel: string): string {
+  return name === "" ? unnamedLabel : name;
+}
+
+export function getTokenRowKey(name: string): string {
+  return name === "" ? "__unnamed_token__" : name;
+}
+
+export function shouldShowTokenTab(detailType: string): boolean {
+  return detailType === "user";
+}
+
+export function getSharePercent(part: number, total: number): number {
+  return total > 0 ? (part / total) * 100 : 0;
+}
+
+export function getPrimaryModelNames(models: DetailBreakdownItem[], limit = 3): string {
+  return models.slice(0, limit).map((model) => model.name || "(unknown)").join(", ");
+}