fix(keys): epic-end review round 1 — Back, menus and dialogs keep the focus where it belongs

Deep-review of E11 (19 raised, 14 confirmed; 2 refuted, 3 latent test-hardening notes dropped).

- Back from a sub-view (a Plex show page, a Messages thread) restores the item it was opened from
  even when focus was still inside the view: the first attempt now waits one task, past the
  sub-view's own popstate listener (measured in Chrome: it left focus on <body>).
- The restore listener is installed at load, so the first Back after a reload finds it; a push
  cancels a restore still waiting for the last landing's lists.
- Navigating over an overlay asks it again, a render apart, while its entry stays: the Plex
  player peels one panel per Back step, so Shift+W over info + stats closed one panel and dropped
  the navigation.
- j/k: a native <button> item keeps its own Tab stop; landing twice on the same item no longer
  leaks its tabindex; after the focused item is removed (a hidden card) the next j goes on from
  its slot when that slot is on screen.
- An abandoned `g` no longer swallows a modifier chord (g, then Mod+K opened the browser search).
- A hover card above a dialog no longer switches its Tab trap off (player, Modal, wizard,
  Lightbox): new layerStack `anyBlockingLayerAbove`.
- "Manage views…" closes its menu before opening the dialog, through a shared `closeThenAct`
  that ActionMenu now uses too.
- Copy: the EN welcome says "Feed"; the EN unreachable reason no longer claims a change;
  stale comments about PlayerModal's scroll lock and dialog contract.

frontend/src/components/Welcome.tsx

@@ -30,7 +30,7 @@ import { setLanguage, type LangCode } from "../i18n";
 import LanguageSwitcher from "./LanguageSwitcher";
 import { Button } from "./ui/Button";
 import { trapTab, useDialogChrome } from "./ui/dialogFocus";
-import { isTopmost, pushLayer, removeLayer } from "../lib/layerStack";
+import { anyBlockingLayerAbove, isTopmost, pushLayer, removeLayer } from "../lib/layerStack";
 import { inputCls } from "./ui/form";
 import { entryHash, entrySearch } from "../lib/entryUrl";
 import type { VerifyEntry } from "../lib/useVerifyEntry";
@@ -275,11 +275,9 @@ function Lightbox({ src, label, onClose }: { src: string; label: string; onClose
   // and the wizard get theirs; the body-scroll lock moved with it, and round 7 added the layer
   // membership below.
   //
-  // It is the THIRD of four to get the contract, not the last: `PlayerModal` is also
-  // `role="dialog" aria-modal="true"` and still hand-rolls its own scroll lock with no accessible
-  // name, no Tab trap and no focus restore. Saying "the fourth shell" here read as though the sweep
-  // were finished, which is the false-completeness that let a demo refusal sit unconverted for a
-  // whole round. It is on ROADMAP.md instead (round 7).
+  // It was the third of four `aria-modal` shells to get the contract; `PlayerModal`, the fourth,
+  // joined in E11 S2, so all four (`ui/Modal`, the wizard, this, the player) now share
+  // `useDialogChrome` and its one counted scroll lock.
   const panelRef = useRef<HTMLDivElement>(null);
   useDialogChrome(panelRef);
   // Keep a stable handler across renders so the stack id is assigned once per mount (as in ui/Modal).
@@ -295,14 +293,14 @@ function Lightbox({ src, label, onClose }: { src: string; label: string; onClose
     // landing page grows (deep-review round 7).
     const id = pushLayer();
     const onKey = (e: KeyboardEvent) => {
-      if (!isTopmost(id)) return;
-      if (e.key === "Escape") {
+      if (e.key === "Escape" && isTopmost(id)) {
         e.stopPropagation();
         onCloseRef.current();
         return;
       }
+      // The trap defers only to a layer that owns the keyboard, not to a hover card under the pointer.
       const panel = panelRef.current;
-      if (e.key === "Tab" && panel) trapTab(e, panel, panel);
+      if (e.key === "Tab" && panel && !anyBlockingLayerAbove(id)) trapTab(e, panel, panel);
     };
     window.addEventListener("keydown", onKey);
     return () => {