web-player: TypeScript helpers (partial)

Add src/lib/actions/pressable.ts and clickOutside.ts (Svelte actions;
role/tabindex stay static in markup for SSR accessibility, the action
only adds click + Enter/Space) and src/lib/toggle.svelte.ts
(createToggle), used by playlists.svelte.ts and queuePanel.svelte.ts.

format.ts: adds plural(n, one, many); migrates the repo's 15 manual
pluralizations, unifying them to lowercase (visible diff in
Playlists, Home, liked, Explore).

player.svelte.ts: adds toQueueItem, isQueueCurrent, playAllOrToggle,
playShuffled; renames addToQueue -> playNextItem (the old name was
misleading: it inserts next, not at the end). Migrates the 5 places
that repeated the isCurrentQueue/playAll pattern (album, playlist,
liked, mix, Home). Simplifies liked.svelte.ts and recentlyPlayed.ts
with object spread instead of rebuilding every field by hand.

navigation.svelte.ts: adds searchHref (migrates the duplicated
buildHref from TopBar and Explore) and appNavLinks (added; its
adoption in Sidebar/TabsBar is left for a later pass, as noted
there).

menus.svelte.ts: createTrackMenu() replaces the manual context-menu
state (contextMenu + contextMenuStateFor + addToQueue) in Home,
Explore and Mix.

Deliberately left pending: removing tracks.ts's TrackTarget wrapper
and its 8 accessors is deferred — it's the riskiest change in the
plan, touches types across Home/Explore/Mix/menus, and couldn't be
visually verified without Docker this session.

Verified with npm run check/build.

web-player/src/lib/components/player/Queue.svelte

@@ -4,6 +4,7 @@
 	import Artwork from '$lib/components/ui/Artwork.svelte';
 	import ArtistLink from '$lib/components/ui/ArtistLink.svelte';
 	import IconButton from '$lib/components/ui/IconButton.svelte';
+	import { pressable } from '$lib/actions/pressable';
 	import { fmtTime } from '$lib/format';
 	import X from '@lucide/svelte/icons/x';
 	import { fly } from 'svelte/transition';
@@ -71,12 +72,7 @@
 				<div
 					role="button"
 					tabindex="0"
-					onclick={() => player.playQueueIndex(index)}
-					onkeydown={(e) => {
-						if (e.key !== 'Enter' && e.key !== ' ') return;
-						e.preventDefault();
-						player.playQueueIndex(index);
-					}}
+					use:pressable={() => player.playQueueIndex(index)}
 					class="flex items-center gap-3 rounded-control p-2.25 text-left hover:bg-hover"
 				>
 					<Artwork trackIds={[track.id]} size="sm" alt={track.title} class="shrink-0 opacity-80" />