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/ROADMAP.md

@@ -102,7 +102,7 @@ Plans:
   2. When the toggle is OFF, access-denied sites produce the same error behavior as before v2.3 (no regression)
   3. When the toggle is ON and a scan hits access denied on a site, the app automatically calls `Tenant.SetSiteAdmin` to elevate ownership and retries the site without interrupting the scan
   4. The scan result for an auto-elevated site is visually distinguishable from a normally-scanned site (e.g., a flag or icon in the results)
-**Plans:** 2 plans
+**Plans:** 1/2 plans executed
 Plans:
 - [ ] 18-01-PLAN.md — Settings toggle + OwnershipElevationService + PermissionEntry.WasAutoElevated flag
 - [ ] 18-02-PLAN.md — Scan-loop elevation logic + DataGrid visual differentiation
@@ -129,5 +129,5 @@ Plans:
 | 15. Consolidation Data Model | v2.3 | 2/2 | Complete | 2026-04-09 |
 | 16. Report Consolidation Toggle | v2.3 | 2/2 | Complete | 2026-04-09 |
 | 17. Group Expansion in HTML Reports | 2/2 | Complete    | 2026-04-09 | — |
-| 18. Auto-Take Ownership | v2.3 | 0/2 | Planned | — |
+| 18. Auto-Take Ownership | 1/2 | In Progress|  | — |
 | 19. App Registration & Removal | v2.3 | 0/? | Not started | — |