feat(ui/agents): add _dayjs helper with relativeTime plugin

Centralizes dayjs.extend(relativeTime) so fromNow() is typed and
loaded across the agents components. relativeOrAbsolute() falls back
to '—' for null/invalid timestamps so callers don't have to
re-implement the guard.

ui/litellm-dashboard/src/app/(dashboard)/agents/components/_dayjs.ts

@@ -0,0 +1,20 @@
+/**
+ * Shared dayjs helper for the cloud-agents dashboard.
+ *
+ * Loads the `relativeTime` plugin once so `dayjs(...).fromNow()` is
+ * typed and works across all the agents components. Without this, the
+ * plugin call is untyped and TS rejects it.
+ */
+import dayjs from "dayjs";
+import relativeTime from "dayjs/plugin/relativeTime";
+
+dayjs.extend(relativeTime);
+
+export function relativeOrAbsolute(value: string | null | undefined): string {
+  if (!value) return "—";
+  const d = dayjs(value);
+  if (!d.isValid()) return "—";
+  return d.fromNow();
+}
+
+export { dayjs };