web: LRU screen cache to bound memory in long sessions (#10063)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/hooks/useWebScrollRestoration.ts

@@ -42,7 +42,11 @@ export function useWebScrollRestoration() {
     () => ({
       focus(e: EventArg<'focus', boolean | undefined, unknown>) {
         const scrollY = state.scrollYs.get(e.target) ?? 0
-        window.scrollTo(0, scrollY)
+        // Deferred so that screens re-mounted by LRU eviction have
+        // time to render their content before we scroll.
+        requestAnimationFrame(() => {
+          window.scrollTo(0, scrollY)
+        })
         state.focusedKey = e.target ?? null
       },
     }),