docs(16-01): complete MergePermissions toggle and consolidated CSV export plan

- 16-01-SUMMARY.md created with all task outcomes and verification results
- STATE.md updated with decisions, session info, progress bar (98%)
- ROADMAP.md updated: phase 16 in-progress (1/2 summaries complete)
- REQUIREMENTS.md: RPT-03 marked complete

.planning/phases/16-report-consolidation-toggle/16-01-SUMMARY.md

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+---
+phase: 16-report-consolidation-toggle
+plan: "01"
+subsystem: export
+tags: [csv-export, consolidation, viewmodel, xaml, localization, tdd]
+dependency-graph:
+  requires: [15-01, 15-02]
+  provides: [MergePermissions toggle UI, consolidated CSV export path]
+  affects: [UserAccessAuditViewModel, PermissionsViewModel, UserAccessCsvExportService]
+tech-stack:
+  added: []
+  patterns: [ObservableProperty, XAML GroupBox binding, optional parameter default, early-return branch, TDD red-green]
+key-files:
+  created: []
+  modified:
+    - SharepointToolbox/ViewModels/Tabs/UserAccessAuditViewModel.cs
+    - SharepointToolbox/ViewModels/Tabs/PermissionsViewModel.cs
+    - SharepointToolbox/Views/Tabs/UserAccessAuditView.xaml
+    - SharepointToolbox/Views/Tabs/PermissionsView.xaml
+    - SharepointToolbox/Localization/Strings.resx
+    - SharepointToolbox/Localization/Strings.fr.resx
+    - SharepointToolbox/Services/Export/UserAccessCsvExportService.cs
+    - SharepointToolbox.Tests/Services/Export/UserAccessCsvExportServiceTests.cs
+decisions:
+  - "Consolidated branch uses early-return pattern inside WriteSingleFileAsync to leave existing code path completely untouched"
+  - "PermissionsViewModel gets MergePermissions as a no-op placeholder — PermissionsViewModel uses a different export service (CsvExportService, not UserAccessCsvExportService) so the property is reserved for future use"
+  - "Export Options GroupBox placed after Scan Options in UserAccessAuditView and after Display Options in PermissionsView — keeps related configuration grouped"
+metrics:
+  duration: ~15min
+  completed: 2026-04-09
+  tasks: 3
+  files-modified: 8
+---
+
+# Phase 16 Plan 01: MergePermissions Toggle UI + Consolidated CSV Export Summary
+
+MergePermissions ObservableProperty on both ViewModels, Export Options GroupBox in both XAML tabs, localized EN/FR strings, and consolidated CSV export path using PermissionConsolidator.
+
+## Tasks Completed
+
+| Task | Name | Commit | Files |
+|------|------|--------|-------|
+| 1 | Add MergePermissions property to both ViewModels and localization keys | ed9f149 | UserAccessAuditViewModel.cs, PermissionsViewModel.cs, Strings.resx, Strings.fr.resx |
+| 2 | Add Export Options GroupBox to both XAML views | db42047 | UserAccessAuditView.xaml, PermissionsView.xaml |
+| 3 (RED) | Add failing tests for RPT-03-f and RPT-03-g | 4f7a6e3 | UserAccessCsvExportServiceTests.cs |
+| 3 (GREEN) | Implement consolidated CSV export path and wire ViewModel call site | 28714fb | UserAccessCsvExportService.cs, UserAccessAuditViewModel.cs |
+
+## What Was Built
+
+### MergePermissions Property
+- `UserAccessAuditViewModel`: `[ObservableProperty] private bool _mergePermissions;` — defaults false, no partial handler needed
+- `PermissionsViewModel`: same property as a no-op placeholder (PermissionsViewModel uses `CsvExportService`, not `UserAccessCsvExportService`)
+
+### Localization
+- `audit.grp.export` — "Export Options" / "Options d'exportation"
+- `chk.merge.permissions` — "Merge duplicate permissions" / "Fusionner les permissions en double"
+
+### XAML GroupBoxes
+Both views received an "Export Options" GroupBox with a single checkbox bound to `MergePermissions`. The groupbox is always visible (never conditionally hidden). Existing XAML elements are untouched.
+
+### Consolidated CSV Export
+`WriteSingleFileAsync` now accepts `bool mergePermissions = false`. When true:
+1. Calls `PermissionConsolidator.Consolidate(entries)` to merge rows sharing the same (UserLogin, PermissionLevel, AccessType, GrantedThrough) key
+2. Writes a consolidated CSV with header: `"User","User Login","Permission Level","Access Type","Granted Through","Locations","Location Count"`
+3. Locations column = semicolon-separated `SiteTitle` values from all merged locations
+4. Returns early — existing code path below is completely untouched
+
+`UserAccessAuditViewModel.ExportCsvAsync` now passes `MergePermissions` to the service.
+
+### Tests (TDD)
+3 new test methods covering RPT-03-f and RPT-03-g:
+- `WriteSingleFileAsync_mergePermissionsfalse_produces_identical_output` — byte-identical to default call
+- `WriteSingleFileAsync_mergePermissionstrue_writes_consolidated_rows` — consolidated header + merged rows
+- `WriteSingleFileAsync_mergePermissionstrue_singleLocation_noSemicolon` — single location has LocationCount=1
+
+All 8 UserAccessCsvExportServiceTests pass.
+
+## Decisions Made
+
+1. **Early-return consolidated branch** — Plan specified leaving existing code path untouched. Added `if (mergePermissions) { ... return; }` before the existing `var sb = new StringBuilder()` block. The existing block is wrapped in an anonymous `{}` scope for clarity but behavior is unchanged.
+
+2. **PermissionsViewModel as no-op placeholder** — The Permissions tab uses `CsvExportService` (not `UserAccessCsvExportService`), so `MergePermissions` cannot be wired to export logic in this plan. The property is added for XAML binding completeness and future implementation.
+
+3. **GroupBox placement** — Export Options placed immediately before the Run/Export buttons in UserAccessAuditView, and before Action buttons in PermissionsView. This keeps export-related options adjacent to export buttons.
+
+## Verification Results
+
+- `dotnet build` — 0 errors, 0 warnings
+- `dotnet test --filter "FullyQualifiedName~UserAccessCsvExportServiceTests"` — 8/8 passed
+- `dotnet test` full suite — 296 passed, 26 skipped, 2 flaky timing failures (pre-existing debounce tests, pass when run individually)
+
+## Deviations from Plan
+
+None — plan executed exactly as written.
+
+## Self-Check: PASSED
+
+Files exist:
+- SharepointToolbox/ViewModels/Tabs/UserAccessAuditViewModel.cs — contains `_mergePermissions`
+- SharepointToolbox/ViewModels/Tabs/PermissionsViewModel.cs — contains `_mergePermissions`
+- SharepointToolbox/Views/Tabs/UserAccessAuditView.xaml — contains `Export Options`
+- SharepointToolbox/Views/Tabs/PermissionsView.xaml — contains `Export Options`
+- SharepointToolbox/Services/Export/UserAccessCsvExportService.cs — contains `mergePermissions`
+- SharepointToolbox.Tests/Services/Export/UserAccessCsvExportServiceTests.cs — 3 new test methods
+
+Commits exist: ed9f149, db42047, 4f7a6e3, 28714fb