test(fase-9): WebKit project + swipe-toggle gesture specs

Closes 9.4 (swipe-delete E2E in WebKit — repurposed to the current
swipe-to-check / swipe-to-uncheck gesture, since Fase 5.10 replaced
swipe-to-delete with a double-tap delete flow).

- playwright.config.ts gains a second project named "webkit"
  (devices['iPhone 13']) gated behind RUN_WEBKIT=1 so the suite stays
  green on hosts that do not have the GTK/WebKit system libs
  (libicu74, libxml2, libmanette-0.2-0, libwoff1) installed — those
  need `sudo pnpm exec playwright install-deps`. The chromium project
  ignores `*.webkit.test.ts` so the same file never runs in both.
- Justfile adds `just playwright-install` (chromium + webkit) and
  `just test-webkit` for the on-demand run.
- New tests/e2e/swipe-toggle.webkit.test.ts contains SW-01 + SW-02:
  swipe right on an unchecked row marks it checked; swipe left on a
  checked row marks it unchecked. The handlers in lists/[id]/+page.svelte
  use unified pointer events, so the helper dispatches
  PointerEvent('pointer{down,move,up}') with pointerType:'touch'
  directly — works regardless of the project's hasTouch setting.
- lists/[id]/+page.svelte exposes data-checked and data-name on each
  item-row to give the specs a robust locator without depending on
  text/heading hierarchy.

Note: cannot validate the WebKit runs end-to-end in this sandbox
(missing libicu74/libwoff1 require sudo apt install). The spec is
ready to run under any CI image that has Playwright's standard
linux deps installed.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/routes/(app)/lists/[id]/+page.svelte

@@ -739,6 +739,8 @@
 									role="listitem"
 									data-testid="item-row"
 									data-selected={isSelected ? 'true' : undefined}
+									data-checked="false"
+									data-name={item.name}
 									class="relative flex items-center gap-2 py-3 select-none transition-transform duration-150 {isSelected ? 'bg-slate-100 dark:bg-slate-800' : 'bg-background'} {selectionMode ? '' : 'touch-pan-y'}"
 									style={selectionMode ? '' : `transform: translateX(${offset}px)`}
 									onpointerdown={(e) => {
@@ -858,6 +860,8 @@
 									role="listitem"
 									data-testid="item-row"
 									data-selected={isSelected ? 'true' : undefined}
+									data-checked="true"
+									data-name={item.name}
 									class="relative flex items-center gap-2 py-3 select-none transition-transform duration-150 {isSelected ? 'bg-slate-100 dark:bg-slate-800' : 'bg-background opacity-70'} {selectionMode ? '' : 'touch-pan-y'}"
 									style={selectionMode ? '' : `transform: translateX(${offset}px)`}
 									onpointerdown={(e) => {