feat: add combineSeries for GPU combination aggregation

src/lib/metrics-poller.ts

@@ -22,6 +22,18 @@ const AGGREGATE: Record<GpuMetricKind, (values: number[]) => number> = {
   fan: avg,
 };
 
+export function combineSeries(histories: number[][], kind: GpuMetricKind): { value?: number; history: number[] } {
+  const n = Math.max(...histories.map((h) => h.length), 0);
+  if (n === 0) return { value: undefined, history: [] };
+  const history: number[] = [];
+  for (let i = 0; i < n; i++) {
+    const at = histories.map((h) => h[i]).filter((v): v is number => v !== undefined);
+    if (at.length === 0) continue;
+    history.push(AGGREGATE[kind](at));
+  }
+  return { value: history.length > 0 ? history[history.length - 1] : undefined, history };
+}
+
 function key(gpuId: string, kind: GpuMetricKind): string {
   return `${gpuId}|${kind}`;
 }