docs(openspec): archive baseline proposals after successful merge

/archive link=https://github.com/fullsizemalt/morethanadiagnosis-hub/pull/1

Complete the OpenSpec lifecycle for all four baseline proposals:
- Architecture Baseline → approved and applied
- Privacy & Compliance Baseline → approved and applied
- Accessibility Baseline → approved and applied
- Wix Migration Plan → approved and applied

All proposals marked as archived with PR traceability.
OpenSpec lifecycle complete: propose → review → apply → archive ✓

openspec/changes/2025-11-17-accessibility-baseline/proposal.md

@@ -1,6 +1,8 @@
 # Proposal: Accessibility Baseline (WCAG 2.2 AA+)
 
-Status: draft
+Status: archived
+Archived: 2025-11-17
+Merged PR: https://github.com/fullsizemalt/morethanadiagnosis-hub/pull/1
 Authors: Accessibility Team
 Owners: Accessibility Lead
 Created: 2025-11-17

openspec/changes/2025-11-17-architecture-baseline/proposal.md

@@ -1,6 +1,8 @@
 # Proposal: Architecture Baseline (v1)
 
-Status: draft
+Status: archived
+Archived: 2025-11-17
+Merged PR: https://github.com/fullsizemalt/morethanadiagnosis-hub/pull/1
 Authors: Core Team
 Owners: Architecture Lead
 Created: 2025-11-17

openspec/changes/2025-11-17-privacy-compliance-baseline/proposal.md

@@ -1,6 +1,8 @@
 # Proposal: Privacy & Compliance Baseline
 
-Status: draft
+Status: archived
+Archived: 2025-11-17
+Merged PR: https://github.com/fullsizemalt/morethanadiagnosis-hub/pull/1
 Authors: Compliance Team
 Owners: Compliance Lead, Security Lead
 Created: 2025-11-17

openspec/changes/2025-11-17-wix-migration-plan/proposal.md

@@ -1,6 +1,8 @@
 # Proposal: Wix Migration Plan (Inventory → Import)
 
-Status: draft
+Status: archived
+Archived: 2025-11-17
+Merged PR: https://github.com/fullsizemalt/morethanadiagnosis-hub/pull/1
 Authors: Data & Content Teams
 Owners: Data Lead, Content Lead
 Created: 2025-11-17