feat: add Reachability Center and Why Drawer components with tests

- Implemented ReachabilityCenterComponent for displaying asset reachability status with summary and filtering options.
- Added ReachabilityWhyDrawerComponent to show detailed reachability evidence and call paths.
- Created unit tests for both components to ensure functionality and correctness.
- Updated accessibility test results for the new components.

docs/api/gateway/samples/policy-simulate-sample.json

@@ -0,0 +1,75 @@
+{
+  "request": {
+    "findings": [
+      {
+        "findingId": "finding-1",
+        "vulnId": "CVE-2024-12345",
+        "componentPurl": "pkg:npm/example@1.2.3",
+        "assetId": "asset::registry.local/ops/auth"
+      }
+    ],
+    "exceptionOverrides": [
+      {
+        "mode": "apply",
+        "exception": {
+          "name": "temporary-risk-acceptance",
+          "severity": "high",
+          "status": "draft",
+          "scope": {
+            "type": "component",
+            "componentPurls": ["pkg:npm/example@1.2.3"],
+            "vulnIds": ["CVE-2024-12345"]
+          },
+          "justification": {
+            "template": "risk-accepted",
+            "text": "What-if analysis for planned remediation."
+          },
+          "timebox": {
+            "startDate": "2025-12-12T00:00:00Z",
+            "endDate": "2025-12-19T00:00:00Z"
+          }
+        }
+      }
+    ]
+  },
+  "response": {
+    "policyVersion": "sha256:policy-demo",
+    "items": [
+      {
+        "findingId": "finding-1",
+        "status": "quieted",
+        "severityBand": "None",
+        "severityScore": 0,
+        "exceptions": [
+          {
+            "schemaVersion": "1.0",
+            "exceptionId": "exc-001",
+            "tenantId": "tenant-default",
+            "name": "temporary-risk-acceptance",
+            "displayName": "Temporary Risk Acceptance",
+            "status": "approved",
+            "severity": "high",
+            "scope": {
+              "type": "component",
+              "componentPurls": ["pkg:npm/example@1.2.3"],
+              "vulnIds": ["CVE-2024-12345"]
+            },
+            "justification": {
+              "template": "risk-accepted",
+              "text": "Approved for demo tenant while remediation is planned."
+            },
+            "timebox": {
+              "startDate": "2025-12-01T00:00:00Z",
+              "endDate": "2025-12-31T23:59:59Z"
+            },
+            "createdBy": "user:demo",
+            "createdAt": "2025-12-01T00:00:00Z"
+          }
+        ]
+      }
+    ],
+    "continuationToken": null,
+    "traceId": "trace-sample-5"
+  }
+}
+