test(admin): probe the statistics endpoints under Yaegi and across replicas

yaegi-check adds probes for these, run under the interpreter against a
fake Redis:
- the last-seen SET reply
- usage/series and usage/totals
- performance with latency on
- catalog price source
- config redaction
- consumers key source
- cache-hit counters

The integration suite adds three checks against two replicas: last seen
is visible across replicas, latency counts match on both, and target
caller totals appear after an MCP call.

Claude-Session: https://claude.ai/code/session_01V5jYJNxpDFdJkyyExpADrv

tools/yaegi-check/main.go

@@ -1007,7 +1007,15 @@ func run() error {
 	// /admin/api/events?limit=1 for the single newest entry right after
 	// producing it, so nothing after it depends on event ordering staying
 	// undisturbed.
-	return exerciseUpstreamAndTimeoutEvents(handler)
+	if err := exerciseUpstreamAndTimeoutEvents(handler); err != nil {
+		return err
+	}
+	// exerciseAdminRedesignStats (admin_redesign.go, admin dashboard
+	// redesign WP-G) runs LAST of all, against its own dedicated Gateway
+	// instance (own config, own fake Redis, own upstream) rather than the
+	// shared `handler` above — see that function's own doc comment for
+	// why.
+	return exerciseAdminRedesignStats(i, pkgName)
 }
 
 // builtinLookupModelID is a real, stable entry in the generated