docs(09-01): complete LiveCharts2 foundation plan

- Add 09-01-SUMMARY.md with task details and self-check
- Update STATE.md position to Phase 9, Plan 1 of 4
- Update ROADMAP.md and REQUIREMENTS.md progress

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.planning/phases/09-storage-visualization/09-01-SUMMARY.md

@@ -0,0 +1,68 @@
+---
+phase: 09-storage-visualization
+plan: 01
+subsystem: storage-visualization
+tags: [nuget, data-model, interface, livecharts2]
+dependency_graph:
+  requires: []
+  provides: [LiveChartsCore.SkiaSharpView.WPF, FileTypeMetric, CollectFileTypeMetricsAsync]
+  affects: [StorageService, StorageVisualization]
+tech_stack:
+  added: [LiveChartsCore.SkiaSharpView.WPF 2.0.0-rc5.4, SkiaSharp 3.116.1]
+  patterns: [record-type-model, interface-extension]
+key_files:
+  created:
+    - SharepointToolbox/Core/Models/FileTypeMetric.cs
+  modified:
+    - SharepointToolbox/SharepointToolbox.csproj
+    - SharepointToolbox/Services/IStorageService.cs
+decisions:
+  - LiveCharts2 RC5.4 with SkiaSharp WPF backend chosen for self-contained EXE compatibility
+  - FileTypeMetric uses record type matching existing model conventions (StorageScanOptions, OperationProgress)
+  - CollectFileTypeMetricsAsync omits StorageScanOptions parameter since file-type scan covers all non-hidden libraries
+metrics:
+  duration: 1 min
+  completed: 2026-04-07
+---
+
+# Phase 09 Plan 01: LiveCharts2, FileTypeMetric Model, and IStorageService Extension Summary
+
+LiveCharts2 SkiaSharp WPF NuGet added, FileTypeMetric record created with Extension/TotalSizeBytes/FileCount/DisplayLabel, IStorageService extended with CollectFileTypeMetricsAsync returning IReadOnlyList<FileTypeMetric>.
+
+## Tasks Completed
+
+| Task | Name | Commit | Key Files |
+|------|------|--------|-----------|
+| 1 | Add LiveCharts2 NuGet and FileTypeMetric model | 60cbb97 | SharepointToolbox.csproj, FileTypeMetric.cs |
+| 2 | Extend IStorageService with CollectFileTypeMetricsAsync | 39c31da | IStorageService.cs |
+
+## Verification Results
+
+- LiveChartsCore.SkiaSharpView.WPF 2.0.0-rc5.4 appears in csproj PackageReference
+- FileTypeMetric.cs exists in Core/Models with record definition (Extension, TotalSizeBytes, FileCount, DisplayLabel)
+- IStorageService.cs has both CollectStorageAsync (unchanged) and CollectFileTypeMetricsAsync (new)
+- Build compiles with 0 errors after Task 1; CS0535 after Task 2 is expected (StorageService implementation deferred to Plan 09-02)
+- NU1701 warnings for OpenTK/SkiaSharp.Views.WPF framework compatibility are non-blocking
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Decisions Made
+
+1. **LiveCharts2 version 2.0.0-rc5.4**: Pre-release RC installed with explicit version flag; no --prerelease fallback needed
+2. **FileTypeMetric as record type**: Matches existing model patterns (StorageScanOptions, OperationProgress) for value semantics
+3. **CollectFileTypeMetricsAsync without StorageScanOptions**: Scans all non-hidden document libraries without folder depth/subsites filtering
+
+## Notes
+
+- NU1701 warnings from OpenTK and SkiaSharp.Views.WPF are expected when targeting net10.0-windows; these packages use .NET Framework fallback but function correctly at runtime
+- CS0535 error is expected and will be resolved in Plan 09-02 when StorageService implements CollectFileTypeMetricsAsync
+
+## Self-Check: PASSED
+
+- All 3 files verified present on disk
+- Both commits (60cbb97, 39c31da) verified in git log
+- LiveChartsCore.SkiaSharpView.WPF in csproj: confirmed
+- CollectFileTypeMetricsAsync in IStorageService.cs: confirmed
+- record FileTypeMetric in FileTypeMetric.cs: confirmed