docs(06-02): complete MainWindowViewModel global site selection plan

- Add 06-02-SUMMARY.md with execution results and dependency graph
- Update STATE.md: progress 20%, decision logged, session recorded
- Update ROADMAP.md: phase 6 in progress (1/5 plans complete)
- Mark SITE-01 requirement complete in REQUIREMENTS.md

.planning/phases/06-global-site-selection/06-02-SUMMARY.md

@@ -0,0 +1,102 @@
+---
+phase: 06-global-site-selection
+plan: 02
+subsystem: ui
+tags: [wpf, mvvm, observable-collection, weak-reference-messenger, community-toolkit]
+
+# Dependency graph
+requires:
+  - phase: 06-global-site-selection/06-01
+    provides: GlobalSitesChangedMessage class in Core/Messages
+provides:
+  - GlobalSelectedSites ObservableCollection on MainWindowViewModel
+  - OpenGlobalSitePickerCommand (disabled when no profile)
+  - GlobalSitesSelectedLabel computed property for toolbar
+  - WeakReferenceMessenger broadcast on GlobalSelectedSites change
+  - Clear on tenant switch and session clear
+affects:
+  - 06-03 (toolbar XAML binds to these properties)
+  - 06-04 (FeatureViewModelBase registers for GlobalSitesChangedMessage)
+
+# Tech tracking
+tech-stack:
+  added: []
+  patterns:
+    - "Func<Window>? factory property for dialog opening (keeps Window refs out of VMs)"
+    - "CollectionChanged subscription to broadcast messenger message and update computed label"
+    - "ObservableCollection clear in OnSelectedProfileChanged for tenant-scoped state"
+
+key-files:
+  created: []
+  modified:
+    - SharepointToolbox/ViewModels/MainWindowViewModel.cs
+
+key-decisions:
+  - "Used using SharepointToolbox.Views.Dialogs in ViewModel for SitePickerDialog cast — acceptable given existing Window reference pattern in this VM"
+  - "GlobalSitesSelectedLabel uses hardcoded string; plan 06-03 will replace with localized keys"
+  - "CollectionChanged event subscribes in constructor to trigger both label update and messenger broadcast atomically"
+
+patterns-established:
+  - "OpenGlobalSitePickerDialog: same Func<Window>? factory pattern as OpenProfileManagementDialog"
+  - "BroadcastGlobalSites(): single helper centralizes messenger send for GlobalSitesChangedMessage"
+
+requirements-completed:
+  - SITE-01
+
+# Metrics
+duration: 8min
+completed: 2026-04-07
+---
+
+# Phase 06 Plan 02: MainWindowViewModel Global Site Selection Summary
+
+**ObservableCollection<SiteInfo> GlobalSelectedSites with dialog command, computed label, messenger broadcast, and clear-on-tenant-switch added to MainWindowViewModel**
+
+## Performance
+
+- **Duration:** 8 min
+- **Started:** 2026-04-07T10:10:00Z
+- **Completed:** 2026-04-07T10:18:00Z
+- **Tasks:** 1
+- **Files modified:** 1
+
+## Accomplishments
+- Added GlobalSelectedSites and OpenGlobalSitePickerCommand to MainWindowViewModel — toolbar UI (06-03) can bind directly
+- WeakReferenceMessenger broadcasts GlobalSitesChangedMessage on every collection change — all tab VMs receive live updates
+- GlobalSelectedSites cleared on tenant switch and session clear, keeping site selection scoped to the current tenant
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Add global site selection state, command, and broadcast to MainWindowViewModel** - `a10f03e` (feat)
+
+**Plan metadata:** _(docs commit to follow)_
+
+## Files Created/Modified
+- `SharepointToolbox/ViewModels/MainWindowViewModel.cs` - Added OpenGlobalSitePickerDialog factory, GlobalSelectedSites, GlobalSitesSelectedLabel, OpenGlobalSitePickerCommand, ExecuteOpenGlobalSitePicker, BroadcastGlobalSites; clear on tenant switch and session clear
+
+## Decisions Made
+- Added `using SharepointToolbox.Views.Dialogs;` to MainWindowViewModel — acceptable because this VM already holds `Func<Window>?` factory properties that reference the View layer. The cast in `ExecuteOpenGlobalSitePicker` requires knowing the concrete dialog type.
+- `GlobalSitesSelectedLabel` uses a hardcoded English string for now; plan 06-03 will replace it with a localized key from Strings.resx once toolbar XAML is added.
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+(Note: `GlobalSitesChangedMessage.cs` was already present from plan 06-01 — no deviation needed.)
+
+## Issues Encountered
+None.
+
+## User Setup Required
+None - no external service configuration required.
+
+## Next Phase Readiness
+- MainWindowViewModel now exposes all properties and commands needed for the toolbar XAML (plan 06-03)
+- `OpenGlobalSitePickerDialog` factory property ready to be wired in MainWindow.xaml.cs (plan 06-03)
+- GlobalSitesChangedMessage broadcasting is live; FeatureViewModelBase can register for it (plan 06-04)
+
+---
+*Phase: 06-global-site-selection*
+*Completed: 2026-04-07*