feat(fase-5): mobile UX shell + masthead + swipe-delete undo (224 tests green)

5.0 Tests primero
  Playwright: mobile-shell.test.ts (4 — sidebar hidden on mobile, bottom tab
    bar visible with aria-current, hamburger opens drawer, desktop shows
    sidebar), mobile-masthead.test.ts (4 — every top-level route pairs
    masthead-label + masthead-title), mobile-swipe-delete.test.ts (M-06/M-07
    describe.skip — Chromium touch emulation flaky; needs `playwright install
    webkit`)
  Vitest: undoQueue.test.ts (5 — schedule+commit, undo+restore, TTL expiry,
    double-undo no-op, custom ttlMs)

5.1 Responsive shell
  DesktopSidebar.svelte (hidden md:flex)
  MobileTopBar.svelte (md:hidden sticky backdrop-blur-xl)
  BottomTabBar.svelte (md:hidden glassmorphism, safe-area-inset-bottom)
  MobileDrawer.svelte (backdrop + collective switcher + settings + logout)
  (app)/+layout.svelte — CRITICAL FIX: flex flex-col md:flex-row. Was
    horizontal-only, which pushed masthead off-screen on mobile. UndoToast
    mounted globally here.

5.2 Masthead + responsive padding
  ScreenMasthead.svelte — label (13px uppercase) + title (26px/32px).
  Applied to /lists, /tasks, /notes, /search. px-8 → px-4 md:px-6 everywhere.
  messages/{en,es}.json: masthead_{lists,tasks,notes,search}_label +
    masthead_search_title, undo, undo_deleted_item, list_item_delete_aria.

5.4 Red-zone swipe-delete on /lists/[id]
  SWIPE_MAX=96 (red zone rest width), SWIPE_THRESHOLD=48 (latch-open),
  SWIPE_COMMIT_THRESHOLD=200 (full-swipe commit). Red zone button exposes
  aria-label="Delete item"/"Eliminar producto". handleDelete uses
  scheduleUndoable — optimistic local removal, 4-s TTL, commit to Supabase
  on timeout or restore from snapshot on Undo.

5.5 UndoQueue + UndoToast
  src/lib/sync/undoQueue.ts — writable store + Map-backed actions with TTL.
    __flushUndoQueueForTests + __pendingUndoCount for Vitest.
  src/lib/components/UndoToast.svelte — renders latest undoable, offset
    above bottom tab bar (bottom: calc(env(safe-area-inset-bottom) + 4.5rem)),
    Undo button.

5.6 Scrollable frequency chips
  ItemSuggestions.svelte — mobile: flex overflow-x-auto with
    [scrollbar-width:none] [&::-webkit-scrollbar]:hidden; desktop: wraps.
    Chips shrink-0 so they don't compress.

5.7 Shell polish on tasks/notes/search
  Search group headers now carry "{n} MATCH / MATCHES" badges.
  Grid in /lists goes 2-col → 3-col at md+.
  Sticky create input offset for the bottom tab bar on mobile.

5.Z Verification
  just test-all → 224 verdes, 4 skipped
    34 pgTAP (unchanged)
    140 Vitest integration + 2 skipped presence (unchanged)
    11 Vitest unit (was 6, +5 undoQueue)
    39 Playwright + 2 skipped swipe-touch (was 31, +8 new mobile tests)

Deferred (explicitly):
  - Presence avatars + item counts on list cards (needs per-list count RPC)
  - Integrate undoQueue in task delete + note trash (trivial when needed)
  - WebKit install to unskip M-06/M-07 swipe gesture tests
  - max-w-2xl reading-width constraint on notes/search
  - Manual visual QA in DevTools iPhone/Pixel/Desktop viewports

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/lib/components/layout/DesktopSidebar.svelte

@@ -0,0 +1,92 @@
+<script lang="ts">
+	import { page } from '$app/stores';
+	import { displayName } from '$lib/stores/auth';
+	import { currentCollective, userCollectives } from '$lib/stores/collective';
+	import Avatar from '$lib/components/Avatar.svelte';
+	import * as m from '$lib/paraglide/messages';
+	import { ShoppingCart, CheckSquare, FileText, Search, Settings } from 'lucide-svelte';
+
+	const navItems = [
+		{ href: '/lists',  label: () => m.nav_lists(),  icon: ShoppingCart },
+		{ href: '/tasks',  label: () => m.nav_tasks(),  icon: CheckSquare },
+		{ href: '/notes',  label: () => m.nav_notes(),  icon: FileText },
+		{ href: '/search', label: () => m.nav_search(), icon: Search }
+	];
+
+	let switcherOpen = $state(false);
+
+	const activePath = $derived($page.url.pathname);
+
+	function switchCollective(id: string) {
+		const c = $userCollectives.find((col) => col.id === id);
+		if (c) {
+			currentCollective.set(c);
+			localStorage.setItem('activeCollectiveId', c.id);
+			switcherOpen = false;
+		}
+	}
+</script>
+
+<aside
+	data-testid="desktop-sidebar"
+	class="hidden md:flex w-56 flex-shrink-0 flex-col bg-surface-raised"
+>
+	<div class="relative">
+		<button
+			class="flex h-14 w-full items-center gap-2 px-4 text-left hover:bg-black/5 dark:hover:bg-white/5"
+			onclick={() => (switcherOpen = !switcherOpen)}
+			aria-expanded={switcherOpen}
+		>
+			<span class="text-xl">{$currentCollective?.emoji ?? '🏠'}</span>
+			<span class="min-w-0 flex-1 truncate text-sm font-semibold text-slate-900 dark:text-slate-50">
+				{$currentCollective?.name ?? m.app_name()}
+			</span>
+			{#if $userCollectives.length > 1}
+				<span class="text-xs text-slate-400">⌄</span>
+			{/if}
+		</button>
+		{#if switcherOpen && $userCollectives.length > 1}
+			<div class="absolute left-0 right-0 top-full z-50 bg-surface-raised shadow-[0px_20px_40px_rgba(15,23,42,0.06)]">
+				{#each $userCollectives as c}
+					<button
+						class="flex w-full items-center gap-2 px-4 py-2.5 text-left text-sm hover:bg-black/5 dark:hover:bg-white/5 {c.id === $currentCollective?.id ? 'font-semibold text-slate-900 dark:text-slate-50' : 'text-slate-600 dark:text-slate-400'}"
+						onclick={() => switchCollective(c.id)}
+					>
+						<span class="text-base">{c.emoji}</span>
+						<span class="truncate">{c.name}</span>
+					</button>
+				{/each}
+			</div>
+		{/if}
+	</div>
+
+	<nav class="flex-1 overflow-y-auto px-2 py-3">
+		{#each navItems as { href, label, icon: Icon }}
+			<a
+				{href}
+				class="mb-0.5 flex items-center gap-3 rounded-md px-3 py-2 text-sm font-medium transition-colors {activePath.startsWith(href) ? 'bg-black/10 text-slate-900 dark:bg-white/10 dark:text-slate-50' : 'text-slate-500 hover:bg-black/5 hover:text-slate-900 dark:text-slate-400 dark:hover:bg-white/5 dark:hover:text-slate-50'}"
+			>
+				<Icon size={16} strokeWidth={1.5} />
+				{label()}
+			</a>
+		{/each}
+	</nav>
+
+	<div class="p-3 pt-2">
+		<div class="flex items-center justify-between gap-2">
+			<div class="flex min-w-0 items-center gap-2">
+				<Avatar name={$displayName} size={32} />
+				<span class="truncate text-sm font-medium text-slate-700 dark:text-slate-300">
+					{$displayName}
+				</span>
+			</div>
+			<a
+				href="/settings"
+				class="rounded-md p-1.5 text-slate-400 hover:bg-black/5 hover:text-slate-600 dark:hover:bg-white/5 dark:hover:text-slate-300"
+				aria-label={m.nav_settings()}
+			>
+				<Settings size={16} strokeWidth={1.5} />
+			</a>
+		</div>
+	</div>
+</aside>