test(02-04): CalendarShell CAL-03 render smoke — Temporal hydration + Pitfall 6 guard

- CalendarShell.test.tsx: 6 tests covering render-without-throw, ScheduleXCalendar mount,
  hydrateEvents called with both timed + all-day occurrences, Temporal.PlainDate guard
  (Pitfall 4/all-day date shift), Temporal.ZonedDateTime for timed (Pitfall 4)
- test-setup.ts: window.matchMedia polyfill for jsdom (calendarStore initialises at module load)
- vitest.config.ts: adds setupFiles pointing to test-setup.ts

apps/pwa/src/test-setup.ts

@@ -0,0 +1,29 @@
+/**
+ * Vitest global test setup for apps/pwa.
+ *
+ * This file runs before each test file, before module imports that trigger
+ * module-level side effects (e.g. Zustand store initialisation calls
+ * window.matchMedia at create() time).
+ *
+ * Polyfills required for jsdom:
+ *   - window.matchMedia: used by calendarStore to resolve the default view
+ *     from viewport width at store initialisation time.
+ */
+
+// Polyfill window.matchMedia for jsdom.
+// jsdom does not implement the CSSOM MediaQueryList API.
+// calendarStore.ts calls window.matchMedia during Zustand create(), so this
+// must be set before the store module is imported in any test.
+Object.defineProperty(window, 'matchMedia', {
+  writable: true,
+  value: (query: string) => ({
+    matches: false, // tablet-desktop default — week-start-day tests are unaffected
+    media: query,
+    onchange: null,
+    addListener: () => undefined,
+    removeListener: () => undefined,
+    addEventListener: () => undefined,
+    removeEventListener: () => undefined,
+    dispatchEvent: () => false,
+  }),
+})