fix(popover): resolve the R8 platform code-review findings

Correctness:
- Escape is now strictly topmost-only for EVERY mode. Hover popovers register in
  the shared layerStack too (and floating-ui's own Escape is off for all modes), so
  an open tooltip/hover-card no longer either swallows the Escape from a Modal/player
  underneath (its document-level stopPropagation vs their window listeners) or
  double-closes both. A player's own overlay hover-card now takes Escape before the
  player, keeping it alive.
- An invisible (referenceHidden, scrolled-out) surface is no longer a dismissable
  layer, so it can't silently eat an Escape aimed at what's actually on screen, nor
  make a player defer.
- PopoverSurface splits into a wrapper that returns null before any hook and an inner
  that holds them, so a mounted-but-closed popover (≈10 per table row) subscribes no
  fullscreen listeners — was ~1800 document listeners on a 100-row table.
- The fullscreen portal no longer remounts on a key: one persistent container is
  re-parented body↔fullscreen-element with appendChild (atomic move), so the open
  panel's focus/caret/scroll/animation survive a transition and an element SWAP is
  handled by the element-identity dependency.
- AddToPlaylist drops `disabled={busy}` on its items (it blurred the focused item to
  <body> and permanently killed roving focus); re-entrancy is already guarded in
  toggle(), and aria-busy conveys the pending state.
- New `hostsInput` option turns off BOTH typeahead and focus-item-on-hover for the two
  menus with an inline text field, so a pointer passing over a list item no longer
  steals the field's caret and mis-routes the next Enter. Replaces their `typeahead:false`.
- ChannelTags' single-pass fit loop gains a whole-set fast path, so it stops collapsing
  chips into "+N" when they would all have fitted.
- `initialFocus={-1}` is applied only when a `selectedIndex` is set (the sync-focus race
  it works around); a plain nav menu now lets the focus manager focus normally, so an
  item-less menu (first-run tag editor) still has a keyboard entry point.

a11y:
- `ariaLabel` now wins on menu-role panels — the surface strips useRole's competing
  `aria-labelledby` when an explicit label is given (verified: the filter/View menus
  are named by their column/label, not the trigger).
- PopoverItem routes caller props THROUGH getItemProps and applies its own
  tabIndex/disabled/data-active/className last, so a caller handler or tabIndex can no
  longer be silently dropped or clobber the roving model.

Regressions / consistency:
- Tooltip shows/hides on contact again (explicit 0/0 hover delay) instead of inheriting
  the platform's 120/140 ms intent delay.
- ChannelTags' editor list regains its useScrollFade overflow mask.
- ChannelTagsControl takes a `bounded` prop; the channel detail page passes false so
  tags show inline in the wide header instead of collapsing to "+N".
- ChannelPage's tag-catalog query is gated on subscribed && !demo (matches the only
  consumer's render condition); the manager's tag toggle now also invalidates
  qk.channel(id) so the detail page's cached tags stay in step.
- DetailCustomizeMenu + PrefToggle revert off the platform to the pre-R8 inline
  `absolute` menu: in the player's overlay it renders inside a transform:scale(1.25)
  subtree, and portalling out to <body> painted it at 1×. Same reason the player's own
  menus stay hand-rolled; this also restores PrefToggle to plain buttons (the rows are
  independent toggles, not a radio group). The stale PlayerModal fullscreen comment is
  corrected too.

Gate green (tsc/eslint/76 vitest). Self-UAT in-browser: hover-over-item no longer
steals the tag input's caret; text filter keeps caret while narrowing; menu aria-label
is the label not the trigger; selectedIndex lands focus on the checked item; roving +
Escape-close+refocus intact; add-to-playlist items never disabled. NOT verified here
(needs a device / playing media): the fullscreen portal reparent and the player-overlay
paths — owed device UAT, as they already were.

frontend/src/components/AddToPlaylist.tsx

@@ -30,7 +30,9 @@ export default function AddToPlaylist({
     open,
     onOpenChange: setOpen,
     offset: 6,
-    typeahead: false,
+    // The menu holds a "new playlist" text field — keep typed chars and pointer-hover out of the
+    // roving list so they don't steal the caret.
+    hostsInput: true,
   });
 
   const membership = useQuery({
@@ -101,7 +103,12 @@ export default function AddToPlaylist({
             would otherwise reach the feed card that hosts the trigger and start playback. */}
         <div onClick={(e) => e.stopPropagation()}>
           <div className="text-xs text-muted px-1.5 pb-1.5">{t("playlists.addToPlaylist")}</div>
-          <div ref={fade.ref} style={fade.style} className="max-h-56 overflow-y-auto no-scrollbar">
+          <div
+            ref={fade.ref}
+            style={fade.style}
+            aria-busy={busy}
+            className="max-h-56 overflow-y-auto no-scrollbar"
+          >
             {lists.length === 0 && !membership.isLoading && (
               <div className="text-xs text-muted px-1.5 py-2">{t("playlists.noneYet")}</div>
             )}
@@ -112,9 +119,12 @@ export default function AddToPlaylist({
                 role="menuitemcheckbox"
                 checked={pl.has_video}
                 onSelect={() => toggle(pl)}
-                disabled={busy}
+                // NOT `disabled={busy}`: the native disabled attribute would blur the focused item to
+                // <body> mid-request and permanently kill roving focus (useListNavigation listens on
+                // the floating element only). `toggle()` already no-ops while busy, so re-entrancy is
+                // guarded without touching focus; `aria-busy` on the list conveys the pending state.
                 label={playlistName(pl, t)}
-                className="w-full flex items-center gap-2 text-sm px-1.5 py-1.5 rounded-lg text-fg outline-none transition hover:bg-card/60 disabled:opacity-50 data-[active]:bg-[color-mix(in_srgb,var(--accent)_24%,transparent)]"
+                className="w-full flex items-center gap-2 text-sm px-1.5 py-1.5 rounded-lg text-fg outline-none transition hover:bg-card/60 data-[active]:bg-[color-mix(in_srgb,var(--accent)_24%,transparent)]"
               >
                 <span
                   className={`grid place-items-center w-4 h-4 rounded border ${