docs(03-03): complete Storage export services plan — CSV and HTML exporters

- Add 03-03-SUMMARY.md: StorageCsvExportService and StorageHtmlExportService
- Update STATE.md: advance to plan 03-04, record metrics and decision
- Update ROADMAP.md: phase 3 progress 3/8 plans complete

.planning/ROADMAP.md

@@ -125,6 +125,6 @@ Phases execute in numeric order: 1 → 2 → 3 → 4 → 5
 |-------|----------------|--------|-----------|
 | 1. Foundation | 8/8 | Complete   | 2026-04-02 |
 | 2. Permissions | 7/7 | Complete | 2026-04-02 |
-| 3. Storage and File Operations | 2/8 | In Progress|  |
+| 3. Storage and File Operations | 3/8 | In Progress|  |
 | 4. Bulk Operations and Provisioning | 0/? | Not started | - |
 | 5. Distribution and Hardening | 0/? | Not started | - |

.planning/STATE.md

@@ -3,15 +3,15 @@ gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
 status: executing
-stopped_at: Completed 03-02-PLAN.md — StorageService CSOM scan engine
+stopped_at: Completed 03-03-PLAN.md — Storage CSV and HTML export services
-last_updated: "2026-04-02T13:28:00.000Z"
+last_updated: "2026-04-02T13:31:45.058Z"
-last_activity: 2026-04-02 — Phase 3 Plan 03-02 complete — StorageService implemented
+last_activity: 2026-04-02 — Plan 03-02 complete — StorageService CSOM scan engine implemented
 progress:
   total_phases: 5
   completed_phases: 2
   total_plans: 23
   completed_plans: 18
-  percent: 78
+  percent: 65
 ---
 
 # Project State
@@ -77,6 +77,7 @@ Progress: [██████░░░░] 65%
 | Phase 02-permissions P06 | 4min | 2 tasks | 6 files |
 | Phase 02-permissions P07 | 30min | 2 tasks | 6 files |
 | Phase 03-storage P01 | 10min | 2 tasks | 22 files |
+| Phase 03-storage P03 | 2min | 2 tasks | 2 files |
 
 ## Accumulated Context
 
@@ -135,6 +136,7 @@ Recent decisions affecting current work:
 - [Phase 03-storage]: Export service stubs return string.Empty until implemented — compile-only skeletons for Plans 03-03 and 03-05
 - [Phase 03-storage 03-02]: StorageService.LastModified uses StorageMetrics.LastModified with fallback to Folder.TimeLastModified — StorageMetrics.LastModified may be DateTime.MinValue for empty libraries
 - [Phase 03-storage 03-02]: System folder filter uses Forms/ and _-prefix heuristic — matches SharePoint standard hidden folder naming convention
+- [Phase 03-storage]: Explicit System.IO using required in StorageCsvExportService and StorageHtmlExportService — WPF project does not include System.IO in implicit usings (established project pattern)
 
 ### Pending Todos
 
@@ -147,6 +149,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-04-02T13:28:00Z
+Last session: 2026-04-02T13:31:45.056Z
-Stopped at: Completed 03-02-PLAN.md — StorageService CSOM scan engine
+Stopped at: Completed 03-03-PLAN.md — Storage CSV and HTML export services
 Resume file: None

.planning/phases/03-storage/03-03-SUMMARY.md

@@ -0,0 +1,126 @@
+---
+phase: 03-storage
+plan: "03"
+subsystem: export
+tags: [csv, html, storage, export, utf8-bom, collapsible-tree]
+
+requires:
+  - phase: 03-02
+    provides: StorageService and StorageNode model with VersionSizeBytes derived property
+
+provides:
+  - StorageCsvExportService.BuildCsv — flat UTF-8 BOM CSV with 6-column header
+  - StorageHtmlExportService.BuildHtml — self-contained HTML with toggle(i) collapsible tree
+  - WriteAsync variants for both exporters
+
+affects:
+  - 03-07 (StorageViewModel wires export buttons to these services)
+  - 03-08 (StorageView integrates export UX)
+
+tech-stack:
+  added: []
+  patterns:
+    - "RFC 4180 Csv() quoting helper — same pattern as Phase 2 CsvExportService"
+    - "HtmlEncode via System.Net.WebUtility.HtmlEncode"
+    - "toggle(i) + sf-{i} ID pattern for collapsible HTML rows"
+    - "_togIdx counter reset at BuildHtml start for unique IDs per call"
+    - "Explicit System.IO using required in WPF project (established pattern)"
+
+key-files:
+  created: []
+  modified:
+    - SharepointToolbox/Services/Export/StorageCsvExportService.cs
+    - SharepointToolbox/Services/Export/StorageHtmlExportService.cs
+
+key-decisions:
+  - "Explicit System.IO using added to StorageCsvExportService and StorageHtmlExportService — WPF project does not include System.IO in implicit usings (existing project pattern)"
+
+patterns-established:
+  - "toggle(i) JS with sf-{i} row IDs for collapsible HTML export — reuse in SearchHtmlExportService (03-05)"
+
+requirements-completed:
+  - STOR-04
+  - STOR-05
+
+duration: 2min
+completed: 2026-04-02
+---
+
+# Phase 03 Plan 03: Storage Export Services — CSV and Collapsible-Tree HTML Summary
+
+**StorageCsvExportService (UTF-8 BOM flat CSV) and StorageHtmlExportService (self-contained collapsible-tree HTML) replace stubs — 6 tests pass**
+
+## Performance
+
+- **Duration:** 2 min
+- **Started:** 2026-04-02T13:29:04Z
+- **Completed:** 2026-04-02T13:30:43Z
+- **Tasks:** 2
+- **Files modified:** 2
+
+## Accomplishments
+
+- StorageCsvExportService.BuildCsv produces UTF-8 BOM CSV with header row: Library, Site, Files, Total Size (MB), Version Size (MB), Last Modified using RFC 4180 quoting
+- StorageHtmlExportService.BuildHtml produces self-contained HTML with inline CSS/JS, toggle(i) function, and collapsible subfolder rows (sf-{i} IDs), ported from PS Export-StorageToHTML
+- All 6 tests pass (3 CSV + 3 HTML)
+
+## Task Commits
+
+1. **Task 1: Implement StorageCsvExportService** - `94ff181` (feat)
+2. **Task 2: Implement StorageHtmlExportService** - `eafaa15` (feat)
+
+## Files Created/Modified
+
+- `SharepointToolbox/Services/Export/StorageCsvExportService.cs` - Full BuildCsv implementation replacing string.Empty stub
+- `SharepointToolbox/Services/Export/StorageHtmlExportService.cs` - Full BuildHtml implementation with collapsible tree rendering
+
+## Decisions Made
+
+- Explicit `System.IO` using added to both files — WPF project does not include System.IO in implicit usings; this is an established project pattern from Phase 1
+
+## Deviations from Plan
+
+### Auto-fixed Issues
+
+**1. [Rule 3 - Blocking] Added explicit System.IO using to StorageCsvExportService**
+- **Found during:** Task 1 (StorageCsvExportService implementation)
+- **Issue:** CS0103 — `File` not found; WPF project lacks System.IO in implicit usings
+- **Fix:** Added `using System.IO;` at top of file
+- **Files modified:** SharepointToolbox/Services/Export/StorageCsvExportService.cs
+- **Verification:** Build succeeded, 3 CSV tests pass
+- **Committed in:** `94ff181` (Task 1 commit)
+
+**2. [Rule 3 - Blocking] Added explicit System.IO using to StorageHtmlExportService**
+- **Found during:** Task 2 (StorageHtmlExportService implementation)
+- **Issue:** Same CS0103 pattern — File.WriteAllTextAsync requires System.IO
+- **Fix:** Added `using System.IO;` preemptively before compilation
+- **Files modified:** SharepointToolbox/Services/Export/StorageHtmlExportService.cs
+- **Verification:** Build succeeded, 3 HTML tests pass
+- **Committed in:** `eafaa15` (Task 2 commit)
+
+---
+
+**Total deviations:** 2 auto-fixed (2 blocking — same root cause: WPF project implicit usings)
+**Impact on plan:** Both fixes necessary for compilation. No scope creep. Consistent with established project pattern.
+
+## Issues Encountered
+
+The `-x` flag passed in the plan's dotnet test command is not a valid MSBuild switch. Omitting it works correctly — documented for future plans.
+
+## User Setup Required
+
+None - no external service configuration required.
+
+## Next Phase Readiness
+
+- StorageCsvExportService and StorageHtmlExportService ready for use by StorageViewModel (Plan 03-07)
+- Both services have WriteAsync variants for file-system output
+- No blockers for Wave 2 parallel execution (03-04, 03-06 can proceed independently)
+
+## Self-Check: PASSED
+
+All files and commits verified present.
+
+---
+*Phase: 03-storage*
+*Completed: 2026-04-02*