docs: update ARCHITECTURE.md with ElastiCache and OpenSearch support

Mark ElastiCache and OpenSearch as implemented (✅) in the architecture
docs, add opensearch.go and helpers.go to the repo structure diagram,
and list all four inventory source implementations.

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

Author: revied

ARCHITECTURE.md

@@ -5,8 +5,8 @@
 **Supported Resources**:
 - ✅ Aurora (RDS MySQL/PostgreSQL)
 - ✅ EKS (Kubernetes)
-- 🔜 ElastiCache (Redis/Valkey/Memcached) - implementation available, needs integration
-- 🔜 OpenSearch
+- ✅ ElastiCache (Redis/Valkey/Memcached)
+- ✅ OpenSearch
 - 🔜 Lambda runtimes
 
 ---
@@ -31,7 +31,7 @@
 **Vision:** Version Guard is a **cloud-agnostic** version drift detection platform supporting multiple cloud providers.
 
 ### Phase 1 (Implemented): AWS
-- **Resources**: ✅ Aurora (RDS), ✅ EKS, 🔜 ElastiCache, 🔜 OpenSearch, 🔜 Lambda
+- **Resources**: ✅ Aurora (RDS), ✅ EKS, ✅ ElastiCache, ✅ OpenSearch, 🔜 Lambda
 - **Inventory**: Wiz (cross-cloud) + AWS APIs
 - **EOL Data**: AWS native APIs (RDS, EKS) + endoflife.date (hybrid enrichment)
 
@@ -116,6 +116,8 @@ Version-Guard/
 │   │   │   ├── aurora.go                 # AWS Aurora inventory
 │   │   │   ├── elasticache.go            # AWS ElastiCache inventory
 │   │   │   ├── eks.go                    # AWS EKS inventory
+│   │   │   ├── opensearch.go             # AWS OpenSearch inventory
+│   │   │   ├── helpers.go                # Shared CSV parsing helpers
 │   │   │   └── client.go                 # Wiz HTTP client
 │   │   └── mock/                         # Mock for tests
 │   │
@@ -137,8 +139,10 @@ Version-Guard/
 │   │   ├── detector.go                   # Detector interface
 │   │   ├── aurora/
 │   │   │   └── detector.go               # Aurora detector
-│   │   └── eks/
-│   │       └── detector.go               # EKS detector
+│   │   ├── eks/
+│   │   │   └── detector.go               # EKS detector
+│   │   └── opensearch/
+│   │       └── detector.go               # OpenSearch detector
 │   │
 │   ├── store/
 │   │   ├── store.go                      # Store interface
@@ -205,6 +209,8 @@ type InventorySource interface {
 **Implementations:**
 - `wiz.AuroraInventorySource` - Wiz saved reports for Aurora
 - `wiz.EKSInventorySource` - Wiz saved reports for EKS
+- `wiz.ElastiCacheInventorySource` - Wiz saved reports for ElastiCache
+- `wiz.OpenSearchInventorySource` - Wiz saved reports for OpenSearch
 - `mock.MockInventorySource` - For testing
 
 **How to extend:**