admin: fix dashboard phantom scroll, drop last-failure column from upstream table

the chart's screen-reader table wore srOnly directly; overflow and
height do not apply to a table box, so it laid out 1200px tall below
the page while clip-path hid the paint. wrap it in a hidden div, which
clips properly and keeps the table role. failure detail is the
diagnostics page's job since milestone 27; the column and the now
dead formatAge go.

admin/src/lib/format.test.ts

@@ -1,4 +1,4 @@
-import { formatAge, formatBytes, formatDuration, formatMicros, formatTime } from "@/lib/format";
+import { formatBytes, formatDuration, formatMicros, formatTime } from "@/lib/format";
 
 test("formatTime renders unix seconds in the given locale and zone", () => {
 	// 2024-01-01T00:00:00Z; ICU emits U+202F before AM/PM in recent Node.
@@ -15,23 +15,19 @@ test("formatBytes humanizes with binary units", () => {
 	expect(formatBytes(2 * 1024 ** 4)).toBe("2.0 TiB");
 });
 
-test("formatAge steps up a unit at each boundary and truncates", () => {
-	expect(formatAge(0)).toBe("0s ago");
-	expect(formatAge(59)).toBe("59s ago");
-	expect(formatAge(60)).toBe("1m ago");
-	expect(formatAge(3599)).toBe("59m ago");
-	expect(formatAge(3600)).toBe("1h ago");
-	expect(formatAge(10800)).toBe("3h ago");
-	expect(formatAge(86399)).toBe("23h ago");
-	expect(formatAge(86400)).toBe("1d ago");
-	expect(formatAge(400000)).toBe("4d ago");
-});
-
-test("formatDuration is the same span without the 'ago', and never negative", () => {
+test("formatDuration steps up a unit at each boundary and truncates", () => {
 	expect(formatDuration(0)).toBe("0s");
 	expect(formatDuration(59)).toBe("59s");
+	expect(formatDuration(60)).toBe("1m");
+	expect(formatDuration(3599)).toBe("59m");
 	expect(formatDuration(3600)).toBe("1h");
+	expect(formatDuration(10800)).toBe("3h");
+	expect(formatDuration(86399)).toBe("23h");
 	expect(formatDuration(86400)).toBe("1d");
+	expect(formatDuration(400000)).toBe("4d");
+});
+
+test("formatDuration is never negative", () => {
 	// Clock skew between the server's timestamps and the browser's clock.
 	expect(formatDuration(-5)).toBe("0s");
 });

admin/src/lib/format.ts

@@ -28,21 +28,9 @@ const AGE_UNITS = [
 ] as const;
 
 /**
- * Seconds of elapsed time → a coarse "3h ago". Truncating and single-unit on
- * purpose: this labels a snapshot the caller renders once, so a reader must not
- * take it for a live count. Nothing re-renders it as it ages.
- */
-export function formatAge(seconds: number): string {
-	for (const unit of AGE_UNITS) {
-		if (seconds >= unit.seconds) return `${Math.floor(seconds / unit.seconds)}${unit.suffix} ago`;
-	}
-	return `${Math.floor(seconds)}s ago`;
-}
-
-/**
- * Seconds of elapsed time → a coarse "3h", the same single truncated unit as
- * `formatAge` without the "ago". For a span the caller labels itself, as in
- * "active for 3h". A negative span reads "0s": clock skew is not a duration.
+ * Seconds of elapsed time → a coarse "3h". Truncating and single-unit on
+ * purpose, for a span the caller labels itself, as in "active for 3h". A
+ * negative span reads "0s": clock skew is not a duration.
  */
 export function formatDuration(seconds: number): string {
 	for (const unit of AGE_UNITS) {