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/advisories.md

@@ -0,0 +1,31 @@
+# Advisory Gateway Contract (draft v0.1)
+
+Scope: proxy Advisory surfaces through the Web gateway with tenant scoping, deterministic responses, ETag caching, and offline-friendly pagination.
+
+## Security / headers
+- `Authorization: Bearer <token>` (or `DPoP` where configured)
+- `X-StellaOps-Tenant: <tenantId>` (required)
+- `X-Stella-Project: <projectId>` (optional)
+- `X-Stella-Trace-Id: <traceId>` (optional; clients SHOULD send one)
+- Scopes: `advisory:read`
+
+## Endpoints
+- `GET /advisories` — list advisories (tenant-scoped).
+  - Query params: `search`, `severity`, `sortBy`, `sortOrder`, `limit`, `continuationToken`
+  - Response: `AdvisoryListResponse` (see sample)
+- `GET /advisories/{advisoryId}` — advisory detail (tenant-scoped).
+
+## Caching & pagination
+- `limit` max: `200`.
+- Cursor/paging uses `continuationToken` (opaque string).
+- `ETag` MUST be a stable hash over a sorted payload; clients MAY send `If-None-Match`.
+- Recommended headers: `Cache-Control: private, max-age=60, stale-if-error=300`.
+
+## Determinism rules
+- Ordering: `items` sorted by `(advisoryId asc)` unless `sortBy` is supplied; ties break by `advisoryId`.
+- Timestamps: ISO-8601 UTC.
+
+## Samples
+- `docs/api/gateway/samples/advisories-list.json`
+- `docs/api/gateway/samples/advisory-detail.json`
+