chore: complete v1.0 milestone

Archive 5 phases (36 plans) to milestones/v1.0-phases/.
Archive roadmap, requirements, and audit to milestones/.
Evolve PROJECT.md with shipped state and validated requirements.
Collapse ROADMAP.md to one-line milestone summary.

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

.planning/RETROSPECTIVE.md

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+# Retrospective
+
+## Milestone: v1.0 — MVP
+
+**Shipped:** 2026-04-07
+**Phases:** 5 | **Plans:** 36 | **Commits:** 164 | **LOC:** 10,071
+
+### What Was Built
+- Complete C#/WPF rewrite replacing 6,400-line PowerShell monolith
+- 10 feature tabs: Permissions, Storage, Search, Duplicates, Transfer, Bulk Members, Bulk Sites, Folder Structure, Templates, Settings
+- Multi-tenant MSAL authentication with per-tenant token caching
+- CSV and interactive HTML export across all scan features
+- Bulk operations with continue-on-error, per-item reporting, retry, and cancellation
+- Self-contained 200 MB EXE with full EN/FR localization (199 keys)
+
+### What Worked
+- **Wave 0 scaffold pattern**: Creating models, interfaces, and test stubs before implementation gave every phase testable targets from day 1
+- **FeatureViewModelBase contract**: Establishing the async/cancel/progress pattern in Phase 1 meant Phases 2-4 had zero friction adding new features
+- **BulkOperationRunner abstraction**: One shared helper gave consistent error semantics across 4 different bulk operations
+- **Phase dependency ordering**: Foundation → Permissions → Storage → Bulk → Hardening prevented rework
+- **Atomic commits per task**: Each plan produced clear, reviewable commit history
+
+### What Was Inefficient
+- **Phase 03 missing verification**: The only phase without a VERIFICATION.md — caught during milestone audit, but should have been produced during execution
+- **Stale audit notes**: Phase 2 verification reported export buttons as hardcoded English, but they were actually already localized by the time of the audit — suggests verification reads code at a point-in-time snapshot that may not reflect later fixes
+- **Cancel test locale mismatch**: The French locale test failure was flagged in Phase 3 plan 08 summary but deferred until post-milestone cleanup — should have been fixed inline
+
+### Patterns Established
+- Write-then-replace JSON persistence with SemaphoreSlim for thread safety
+- TranslationSource singleton with PropertyChanged(string.Empty) for runtime culture switching
+- ExecuteQueryRetryHelper for throttle-aware CSOM calls (429/503 detection)
+- SharePointPaginationHelper with ListItemCollectionPosition for 5,000+ item lists
+- CsvValidationService with auto-delimiter detection (comma/semicolon) and BOM handling
+- DataGrid RowStyle DataTrigger for invalid-row visual highlighting
+
+### Key Lessons
+- Establish shared infrastructure patterns (auth, retry, pagination, progress) in Phase 1 — every subsequent phase benefits
+- Test scaffolds (Wave 0) eliminate the "no tests until the end" anti-pattern
+- Phase verifications should be mandatory during execution, not optional — catching Phase 03's gap at audit time is late
+- Localization tests (key parity + diacritic spot-checks) are cheap and catch real bugs
+
+---
+
+## Cross-Milestone Trends
+
+| Metric | v1.0 |
+|--------|------|
+| Phases | 5 |
+| Plans | 36 |
+| LOC | 10,071 |
+| Tests | 134 pass / 22 skip |
+| Timeline | 28 days |
+| Commits | 164 |