fix(02): remove custom ViewToolbar; use Schedule-X built-in header

- Remove <ViewToolbar> render and its import from CalendarShell
- Remove createCalendarControlsPlugin import, useState instance, and plugin
  array entry (calendar-controls only served the custom toolbar)
- Delete ViewToolbar.tsx (no longer referenced anywhere)
- Remove calendar-controls mock from CalendarShell.test.tsx
- CSS audit confirmed no rules hide Schedule-X weekday-name row; no CSS changes needed
- All four views (day/week/month-grid/month-agenda) remain; Schedule-X's native
  header exposes them in its own view switcher

apps/pwa/src/components/CalendarShell.tsx

@@ -14,10 +14,12 @@
  *   - Event popover: driven exclusively by Zustand openEventId via onEventClick → standalone
  *     EventDetailPopover; createEventModalPlugin and customComponents.eventModal are NOT used
  *   - Threat T-02d-01: all event fields are plain-text JSX children — no raw HTML injection
+ *   - Navigation: Schedule-X's built-in header is the sole navigation bar (Today/‹›/view switcher
+ *     + weekday-name row). The custom ViewToolbar and calendar-controls plugin have been removed.
  *
  * Layout:
- *   - Phone (≤767px): AppNav top bar → ViewToolbar → calendar grid (primary focal point)
- *   - Tablet/Desktop (≥768px): AppNav left sidebar (240px) + main area (ViewToolbar + grid)
+ *   - Phone (≤767px): AppNav top bar → Schedule-X (header + grid)
+ *   - Tablet/Desktop (≥768px): AppNav left sidebar (240px) + main area (Schedule-X header + grid)
  *
  * State branches:
  *   isLoading (initial) → SkeletonCalendar
@@ -37,7 +39,6 @@ import {
   type CalendarType,
 } from '@schedule-x/calendar'
 import { createEventsServicePlugin } from '@schedule-x/events-service'
-import { createCalendarControlsPlugin } from '@schedule-x/calendar-controls'
 
 import { fetchMe, fetchEvents } from '../api/client.js'
 import { hydrateEvents } from '../lib/hydrateEvents.js'
@@ -45,7 +46,6 @@ import { buildCalendarConfig, SX_FIRST_DAY_OF_WEEK } from '../lib/calendarConfig
 import { useCalendarStore } from '../store/calendarStore.js'
 import { EventDetailPopover } from './EventDetailPopover.js'
 import { AppNav } from './AppNav.js'
-import { ViewToolbar } from './ViewToolbar.js'
 import { ColorLegend } from './ColorLegend.js'
 import { SkeletonCalendar } from './SkeletonCalendar.js'
 import { EmptyState } from './EmptyState.js'
@@ -96,7 +96,6 @@ export function CalendarShell() {
 
   // Create plugins once (stable across renders)
   const eventsService = useState(() => createEventsServicePlugin())[0]
-  const calendarControls = useState(() => createCalendarControlsPlugin())[0]
 
   // Build members list from /api/me for AppNav + ColorLegend
   const members = useMemo(() => {
@@ -148,7 +147,7 @@ export function CalendarShell() {
         },
       },
     },
-    [eventsService, calendarControls],
+    [eventsService],
   )
 
   // Sync TanStack Query result into Schedule-X eventsService (Pitfall 4 guard)
@@ -205,9 +204,6 @@ export function CalendarShell() {
           overflow: 'hidden',
         }}
       >
-        {/* ViewToolbar */}
-        <ViewToolbar controls={calendarControls} />
-
         {/* Main calendar area */}
         <div style={{ flex: 1, minHeight: 0, position: 'relative', overflow: 'hidden' }}>
           {isInitialLoading ? (