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/ROADMAP.md

@@ -36,7 +36,7 @@
   2. Selecting sites in the toolbar causes all feature tabs to default to those sites when an operation is run
   3. A user can override the global selection on any individual tab without clearing the global state
   4. The global site selection persists across tab switches within the same session
-**Plans:** 5 plans
+**Plans:** 1/5 plans executed
 Plans:
 - [ ] 06-01-PLAN.md — GlobalSitesChangedMessage + FeatureViewModelBase extension
 - [ ] 06-02-PLAN.md — MainWindowViewModel global selection state + command
@@ -86,7 +86,7 @@ Plans:
 | 3. Storage and File Operations | v1.0 | 8/8 | Complete | 2026-04-02 |
 | 4. Bulk Operations and Provisioning | v1.0 | 10/10 | Complete | 2026-04-03 |
 | 5. Distribution and Hardening | v1.0 | 3/3 | Complete | 2026-04-03 |
-| 6. Global Site Selection | v1.1 | 0/5 | Planned | - |
+| 6. Global Site Selection | 1/5 | In Progress|  | - |
 | 7. User Access Audit | v1.1 | 0/? | Not started | - |
 | 8. Simplified Permissions | v1.1 | 0/? | Not started | - |
 | 9. Storage Visualization | v1.1 | 0/? | Not started | - |