feat(design): a playlist's one action list (C1) — the row's "…", Delete + undo, the header's "…" (E28 S3e2)

- Playlist rows: the X column became the row's "…" (play, pin, copy title/link, move, order,
  remove). Remove runs at once, with no confirm; its toast's Undo puts the row back at its index.
  The Delete key removes a keyboard-walked row, and focus moves on to the next.
- POST /api/playlists/{id}/items takes an optional `position`, so an undo is one request that
  renumbers the list around the row.
- A new `listDelete` key scope. Only a list with `onDelete` registers it, so the help sheet does not
  offer Delete where nothing handles it.
- A playlist has one list, `usePlaylistActions.items`: rename, pin, YouTube open/push/revert,
  delete. The rail row's "…" and the page header's "…" both open it. Push and revert moved into
  the hook; the header keeps Play all.
- Phone-width playlist table: "#" and Channel are hidden below sm (`Column.phoneHidden`). Their
  fixed widths had left the title no width.

frontend/src/i18n/locales/en/keys.json

@@ -35,6 +35,7 @@
   "listStep": "Next / previous item",
   "gridMove": "Move around the list",
   "open": "Open the selected item",
+  "listRemove": "Remove the selected item from the list",
   "cap": {
     "space": "Space",
     "menu": "Menu"

frontend/src/i18n/locales/en/playlists.json

@@ -75,6 +75,8 @@
   "moveNoTargets": "There is no other playlist to move it to yet.",
   "movedToast": "“{{title}}” moved to “{{name}}” ✓",
   "moveFailed": "Couldn't move the video.",
+  "removedToast": "“{{title}}” removed from the playlist",
+  "undoRemoveFailed": "Couldn't put the video back.",
   "removeFailed": "Couldn't remove the video.",
   "errors": {
     "name_required": "Give the playlist a name.",
@@ -97,7 +99,6 @@
   "builtinLocked": "The built-in {{name}} list can’t be renamed or deleted.",
   "removeItem": "Remove",
   "removeItemOf": "Remove “{{title}}” from the playlist",
-  "confirmRemove": "Remove “{{title}}” from this playlist?",
   "dragHandleOf": "Reorder “{{title}}”",
   "dragBlockedSort": "Reordering by hand is off while a column sort or grouping is applied.",
   "dragBlockedFilter": "Reordering by hand is off while a filter is applied.",

frontend/src/i18n/locales/hu/keys.json

@@ -35,6 +35,7 @@
   "listStep": "Következő / előző elem",
   "gridMove": "Mozgás a listában",
   "open": "A kijelölt elem megnyitása",
+  "listRemove": "A kijelölt elem eltávolítása a listából",
   "cap": {
     "space": "Szóköz",
     "menu": "Menü"

frontend/src/i18n/locales/hu/playlists.json

@@ -75,6 +75,8 @@
   "moveNoTargets": "Még nincs másik lejátszási lista, ahová áthelyezhetnéd.",
   "movedToast": "„{{title}}” áthelyezve ide: „{{name}}” ✓",
   "moveFailed": "Nem sikerült áthelyezni a videót.",
+  "removedToast": "„{{title}}” eltávolítva a listáról",
+  "undoRemoveFailed": "Nem sikerült visszatenni a videót.",
   "removeFailed": "Nem sikerült eltávolítani a videót.",
   "errors": {
     "name_required": "Adj nevet a lejátszási listának.",
@@ -97,7 +99,6 @@
   "builtinLocked": "A beépített „{{name}}” lista nem nevezhető át és nem törölhető.",
   "removeItem": "Eltávolítás",
   "removeItemOf": "„{{title}}” eltávolítása a listáról",
-  "confirmRemove": "Eltávolítod a(z) „{{title}}” videót erről a listáról?",
   "dragHandleOf": "„{{title}}” átrendezése",
   "dragBlockedSort": "A kézi átrendezés ki van kapcsolva, amíg oszloprendezés vagy csoportosítás van érvényben.",
   "dragBlockedFilter": "A kézi átrendezés ki van kapcsolva, amíg szűrő van érvényben.",