One elapsed-time notation: ago() reads dur's units app-wide, health runs cell widened

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

frontend/src/lib/utils.ts

@@ -81,3 +81,13 @@ export function dur(ms: number, digits = 3): string {
   ]
   return `${Number((rounded / factor).toPrecision(digits))} ${unit}`
 }
+
+/**
+ * How long ago a moment was, in `dur`'s notation: "4.52 min ago". A number is
+ * unix seconds, a string an ISO timestamp.
+ */
+export function ago(ts: string | number | null | undefined): string {
+  if (!ts) return "—"
+  const stamp = typeof ts === "number" ? ts * 1000 : Date.parse(ts)
+  return `${dur(Math.max(0, Date.now() - stamp))} ago`
+}