feat(playlists): select rows with a box, Shift for a range, x and Esc

A box first in every row and one over the column for the rows shown, the
selected row tinted. A filter keeps what it hides selected; another list
starts over; a row that left the list drops out. Watch later has none.

A box no longer counts as a typing target: a click on one left the focus
there and the page's keys went dead.

docs/DESIGN.md

@@ -536,6 +536,11 @@ of a full-width panel and nothing on the right.
   shows them as four buttons with the item's place beside the selected view; a side panel in edit mode
   gives each group an Up / Down pair (`ui/OrderButtons`, `compact`). A move that would go nowhere is
   shown off, not hidden. A grip also picks up from the keyboard (space, the arrows, space).
+- **Selecting rows:** a list whose rows take bulk actions shows a box first in every row, always, and one
+  over the column for the rows shown. Shift+click selects a range, `x` toggles the row under the keyboard,
+  Esc clears. A selected row wears the accent tint as well as its tick. An action covers the selected rows
+  shown; a row a filter hides stays selected and comes back ticked; another list starts over. The row's own
+  menu still acts on that row alone.
 - **Motion:** 150–300ms micro-interactions, transform/opacity only; `prefers-reduced-motion` is respected.
   [WCAG 2.3.3]
 
@@ -834,3 +839,4 @@ of a full-width panel and nothing on the right.
 | 2026-11-01 | Channel header on a tablet (owner E2)            | Below `xl` the action row drops its two words: "Prio" (the stepper's tooltip names it) and "Subscribed" (a ✓ glyph; its name in the aria-label, Unsubscribe in the tooltip); the tags keep the row's rest, folding into "+N"                                                                                                                                                                        | The tag lane on a full line of its own below ~12rem; the tags under the channel name                                                                                                                   | On an iPad (820 px, 44 px targets) the lane got 29 px, a sliver; now 130 px, and every tag shows at 1180                                                                                                                     |
 | 2026-11-01 | Clear watch progress (owner E a)                 | A video menu's Reset reads "Clear watch progress" in English (HU "Megtekintés visszaállítása" stays); "Reset view" is only a page's view reset (sort, filters, grouping)                                                                                                                                                                                                                            | "Reset view" for both; the playlist page's view reset renamed instead                                                                                                                                  | On a playlist page the two stood one right-click apart under one name, and one of them erases the video's progress with no undo                                                                                              |
 | 2026-11-01 | Clear watch progress clears only that (owner A)  | The row shows only on a video with a resume point and clears that alone: a hidden video stays hidden, a watched one watched. Un-hiding and un-watching have rows of their own                                                                                                                                                                                                                       |
+| 2026-11-01 | Selecting a list's rows (owner D2 a)             | An always visible box first in the row and one over the column for the rows shown; Shift+click a range, `x` the row under the keyboard, Esc clears; the selected row wears `accent/12` with its tick. Rows a filter hides stay selected, an action covers those shown; Watch later offers no selecting. |