docs(18-01): complete auto-take-ownership settings foundation plan

- 18-01-SUMMARY.md: plan execution summary
- STATE.md: progress updated to 98%, decisions recorded, stopped-at updated
- ROADMAP.md: phase 18 marked in-progress (1/2 summaries)
- REQUIREMENTS.md: OWN-01 marked complete

.planning/phases/18-auto-take-ownership/18-01-SUMMARY.md

@@ -0,0 +1,83 @@
+---
+phase: 18-auto-take-ownership
+plan: "01"
+subsystem: settings, models, services
+tags: [auto-take-ownership, settings, permission-entry, elevation-service, di]
+dependency_graph:
+  requires: []
+  provides: [AppSettings.AutoTakeOwnership, PermissionEntry.WasAutoElevated, IOwnershipElevationService, OwnershipElevationService, SettingsViewModel.AutoTakeOwnership]
+  affects: [SharepointToolbox/Core/Models/AppSettings.cs, SharepointToolbox/Core/Models/PermissionEntry.cs, SharepointToolbox/Services/SettingsService.cs, SharepointToolbox/ViewModels/Tabs/SettingsViewModel.cs, SharepointToolbox/Views/Tabs/SettingsView.xaml]
+tech_stack:
+  added: [IOwnershipElevationService, OwnershipElevationService, Microsoft.Online.SharePoint.TenantAdministration.Tenant.SetSiteAdmin]
+  patterns: [fire-and-forget property setter pattern (matching DataFolder), DI transient registration]
+key_files:
+  created:
+    - SharepointToolbox/Services/IOwnershipElevationService.cs
+    - SharepointToolbox/Services/OwnershipElevationService.cs
+    - SharepointToolbox.Tests/Services/OwnershipElevationServiceTests.cs
+    - SharepointToolbox.Tests/ViewModels/SettingsViewModelOwnershipTests.cs
+  modified:
+    - SharepointToolbox/Core/Models/AppSettings.cs
+    - SharepointToolbox/Core/Models/PermissionEntry.cs
+    - SharepointToolbox/Services/SettingsService.cs
+    - SharepointToolbox/ViewModels/Tabs/SettingsViewModel.cs
+    - SharepointToolbox/Views/Tabs/SettingsView.xaml
+    - SharepointToolbox/Localization/Strings.resx
+    - SharepointToolbox/Localization/Strings.fr.resx
+    - SharepointToolbox/App.xaml.cs
+decisions:
+  - "OwnershipElevationService.ElevateAsync uses Tenant.SetSiteAdmin from PnP.Framework (Microsoft.Online.SharePoint.TenantAdministration)"
+  - "WasAutoElevated placed last with default=false in PermissionEntry positional record to avoid breaking all existing callsites"
+  - "AutoTakeOwnership in SettingsViewModel follows fire-and-forget pattern matching DataFolder setter"
+metrics:
+  duration: "~15 minutes"
+  tasks_completed: 2
+  files_modified: 8
+  files_created: 4
+  completed_date: "2026-04-09"
+---
+
+# Phase 18 Plan 01: Auto-Take Ownership Settings Foundation Summary
+
+**One-liner:** AppSettings, PermissionEntry, IOwnershipElevationService/impl, and SettingsView checkbox for auto-take-ownership toggle backed by full EN/FR localization and 10 new tests.
+
+## Tasks Completed
+
+| Task | Name | Commit | Files |
+|------|------|--------|-------|
+| 1 | Models + SettingsService + OwnershipElevationService + tests | 36fb312 | AppSettings.cs, PermissionEntry.cs, SettingsService.cs, IOwnershipElevationService.cs, OwnershipElevationService.cs, SettingsViewModel.cs, App.xaml.cs, 2 test files |
+| 2 | SettingsView XAML + localization | 20948e4 | SettingsView.xaml, Strings.resx, Strings.fr.resx |
+
+## What Was Built
+
+- `AppSettings.AutoTakeOwnership` bool property defaulting to `false`, round-trips through JSON.
+- `PermissionEntry.WasAutoElevated` optional positional parameter (last, default `false`) — zero callsite breakage.
+- `SettingsService.SetAutoTakeOwnershipAsync(bool)` persists toggle following same pattern as `SetLanguageAsync`/`SetDataFolderAsync`.
+- `IOwnershipElevationService` interface with `ElevateAsync(ClientContext, siteUrl, loginName, ct)`.
+- `OwnershipElevationService` wraps `Tenant.SetSiteAdmin` from PnP.Framework.
+- DI registration: `services.AddTransient<IOwnershipElevationService, OwnershipElevationService>()` in App.xaml.cs.
+- `SettingsViewModel.AutoTakeOwnership` property loads from settings on `LoadAsync()`, persists on set via fire-and-forget `SetAutoTakeOwnershipAsync`.
+- `SettingsView.xaml` "Site Ownership" section with `CheckBox` bound to `AutoTakeOwnership`, with description `TextBlock`.
+- EN/FR localization keys: `settings.ownership.title`, `settings.ownership.auto`, `settings.ownership.description`.
+- 10 new tests covering all behaviors; full suite: 328 passed, 28 skipped, 0 failed.
+
+## Decisions Made
+
+1. `OwnershipElevationService.ElevateAsync` uses `Tenant.SetSiteAdmin` (already available via PnP.Framework `Microsoft.Online.SharePoint.TenantAdministration`).
+2. `WasAutoElevated` placed last with `= false` default in the positional record — no existing callsite needed updating.
+3. `AutoTakeOwnership` ViewModel setter uses `_ = _settingsService.SetAutoTakeOwnershipAsync(value)` matching the `DataFolder` fire-and-forget pattern.
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Test Results
+
+- `dotnet build SharepointToolbox.slnx` — 0 errors, 0 warnings
+- `dotnet test ... --filter OwnershipElevation|SettingsViewModelOwnership` — 8/8 passed
+- `dotnet test ... --filter LocaleCompleteness` — 2/2 passed
+- Full suite — 328 passed, 0 failed, 28 skipped
+
+## Self-Check: PASSED
+
+All created files exist. All commits verified. Full test suite green.