fix(web): stop Sidebar re-render loop from cache-event subscriber

setNow(Date.now()) was called on every query-cache event, including
events dispatched synchronously during ServerWorkspaceRows' render.
On CI, consecutive Date.now() calls cross millisecond boundaries so
each call returns a new value — React always re-renders Sidebar, which
re-renders the layout, which re-renders ServerWorkspaceRows, which
fires more cache events. After ~25 cycles React throws "Maximum update
depth exceeded."

Fix: remove setNow from the cache subscriber. setNow now fires only
from the 30s interval timer, where it correctly refreshes the "X ago"
display text without triggering a render loop.

Also adds a deterministic CI-repro test that mocks Date.now to return
incrementing values and asserts the filter-change path completes without
looping.

packages/web/src/components/layout/Sidebar.tsx

@@ -60,7 +60,9 @@ function useLastDataUpdate(): string {
 
 	useEffect(() => {
 		function refresh() {
-			setNow(Date.now());
+			// No setNow here — calling setNow on every cache event causes a render loop on
+			// CI (each Date.now() call crosses a ms boundary → new value → React re-renders
+			// Sidebar → cache events fire again → loop). setNow belongs only in the interval.
 			const latest = queryClient
 				.getQueryCache()
 				.getAll()
@@ -70,7 +72,10 @@ function useLastDataUpdate(): string {
 
 		refresh();
 		const unsubscribe = queryClient.getQueryCache().subscribe(refresh);
-		const interval = window.setInterval(refresh, 30_000);
+		const interval = window.setInterval(() => {
+			setNow(Date.now()); // refresh relative-time display ("X ago") every 30s
+			refresh();
+		}, 30_000);
 		return () => {
 			unsubscribe();
 			window.clearInterval(interval);