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/ui/AnchoredPopover.tsx

@@ -393,6 +393,18 @@ const HIGHLIGHT_SELECTED =
 const HIGHLIGHT_SELECTED_RING_ONLY =
   "data-active:ring-2 data-active:ring-inset data-active:ring-accent/70";
 
+/** A menu row whose action opens a dialog or moves the focus: close the menu FIRST and act once it
+ *  has handed the focus back. floating-ui returns the focus to the trigger from a microtask queued as
+ *  the menu unmounts, so an action run in the same batch had its focus taken back by it: measured in
+ *  Chrome (E11 S2), a confirm dialog opened from the rail's menu landed its focus on Cancel and lost it
+ *  7 ms later to the row BEHIND its scrim, where Enter activated the row. A fresh task runs after that
+ *  microtask — and a dialog opened there captures the trigger, not a dying menu item, as the element
+ *  to restore the focus to. Every such row goes through here (`ActionMenu`, "Manage views…"). */
+export function closeThenAct(close: () => void, act: () => void): void {
+  close();
+  setTimeout(act, 0);
+}
+
 export function PopoverItem({
   children,
   onSelect,