docs(07-03): complete GraphUserSearchService plan

- Add 07-03-SUMMARY.md with implementation details and decisions
- Update STATE.md: progress 54%, decisions, session, metrics
- Update ROADMAP.md: phase 07 now 2/8 summaries

.planning/phases/07-user-access-audit/07-03-SUMMARY.md

@@ -0,0 +1,69 @@
+---
+phase: 07-user-access-audit
+plan: 03
+subsystem: graph-user-search-service
+tags: [graph-api, user-search, people-picker, services]
+dependency_graph:
+  requires: [07-01]
+  provides: [GraphUserSearchService]
+  affects: [07-04, 07-05]
+tech_stack:
+  added: []
+  patterns: [Microsoft Graph SDK, OData filter, startsWith, ConsistencyLevel=eventual]
+key_files:
+  created:
+    - SharepointToolbox/Services/GraphUserSearchService.cs
+  modified: []
+decisions:
+  - "Minimum 2-character query guard prevents overly broad Graph API requests"
+  - "Single-quote escaping in OData filter prevents injection (replace ' with '')"
+  - "ConsistencyLevel=eventual + Count=true both required for startsWith on directory objects"
+metrics:
+  duration_minutes: 2
+  completed_date: "2026-04-07"
+  tasks_completed: 1
+  files_created: 1
+  files_modified: 0
+---
+
+# Phase 7 Plan 03: GraphUserSearchService Implementation Summary
+
+**One-liner:** GraphUserSearchService implements IGraphUserSearchService using GraphClientFactory, querying Graph /users with startsWith OData filter on displayName, mail, and UPN for people-picker autocomplete.
+
+## What Was Built
+
+**GraphUserSearchService.cs** — Concrete implementation of IGraphUserSearchService. Queries the Microsoft Graph `/users` endpoint using OData `startsWith` filter across three fields (displayName, mail, userPrincipalName). Sets the required `ConsistencyLevel: eventual` header and `$count=true` parameter mandatory for advanced directory filters. Returns up to `maxResults` (default 10) `GraphUserResult` records ordered by displayName. Guards against queries shorter than 2 characters to prevent broad, wasteful API calls.
+
+## Tasks
+
+| # | Task | Status | Commit |
+|---|------|--------|--------|
+| 1 | Implement GraphUserSearchService | Done | 026b829 |
+
+## Decisions Made
+
+1. **2-character minimum guard** — Queries of 0 or 1 character return an empty list immediately without calling Graph. This prevents overly broad results and unnecessary API calls while the user is still typing.
+
+2. **OData single-quote escaping** — Query strings replace `'` with `''` before embedding in the OData filter. This prevents OData injection if user input contains apostrophes (e.g., "O'Brien").
+
+3. **ConsistencyLevel=eventual + Count=true** — Microsoft Graph requires both headers when using `startsWith` on directory objects. Omitting either causes a 400 Bad Request. Both are set together in the request configuration.
+
+## Deviations from Plan
+
+None — plan executed exactly as written.
+
+## Verification
+
+- `dotnet build SharepointToolbox/SharepointToolbox.csproj` — 0 errors, 0 warnings
+- GraphUserSearchService.cs implements IGraphUserSearchService confirmed
+- Uses GraphClientFactory.CreateClientAsync for auth (not raw HTTP)
+- Empty/short query guard (length < 2) returns Array.Empty<GraphUserResult>()
+- Filter covers displayName, mail, and userPrincipalName with startsWith
+
+## Self-Check: PASSED
+
+Files confirmed present:
+- FOUND: SharepointToolbox/Services/GraphUserSearchService.cs
+
+Commits confirmed:
+- FOUND: 026b829