Add Canonical JSON serialization library with tests and documentation

- Implemented CanonJson class for deterministic JSON serialization and hashing.
- Added unit tests for CanonJson functionality, covering various scenarios including key sorting, handling of nested objects, arrays, and special characters.
- Created project files for the Canonical JSON library and its tests, including necessary package references.
- Added README.md for library usage and API reference.
- Introduced RabbitMqIntegrationFactAttribute for conditional RabbitMQ integration tests.

src/Web/StellaOps.Web/AGENTS.md

@@ -18,6 +18,45 @@ Design and build the StellaOps web user experience that surfaces backend capabil
 - `docs/` — UX specs and mockups (to be added).
 - `ops/` — Web deployment manifests for air-gapped environments (future).
 
+## Reachability Drift UI (Sprint 3600)
+
+### Components
+- **PathViewerComponent** (`app/features/reachability/components/path-viewer/`) - Interactive call path visualization
+  - Displays entrypoint → key nodes → sink paths
+  - Highlights changed nodes with change kind indicators
+  - Supports collapse/expand for long paths
+- **RiskDriftCardComponent** (`app/features/reachability/components/risk-drift-card/`) - Summary card for drift analysis
+  - Shows newly reachable / mitigated path counts
+  - Displays associated CVEs
+  - Action buttons for drill-down
+
+### Models
+- `PathNode` - Node in a reachability path with symbol, file, line
+- `CompressedPath` - Compact path representation
+- `DriftedSink` - Sink with reachability change and cause
+- `DriftCause` - Explanation of why reachability changed
+
+### Services
+- `DriftApiService` (`app/core/services/drift-api.service.ts`) - API client for drift endpoints
+- Mock implementations available for offline development
+
+### Integration Points
+- Scan detail page includes PathViewer for reachability visualization
+- Drift results linked to DSSE attestations for evidence chain
+- Path export supports JSON and SARIF formats
+
+## Witness UI (Sprint 3700) - TODO
+
+### Planned Components
+- **WitnessModalComponent** - Modal for viewing witness details
+- **PathVisualizationComponent** - Detailed path rendering with gates
+- **ConfidenceTierBadgeComponent** - Tier indicators (Confirmed/Likely/Present/Unreachable)
+- **GateBadgeComponent** - Auth gate visualization
+
+### Planned Services
+- `witness.service.ts` - API client for witness endpoints
+- Browser-based Ed25519 signature verification
+
 ## Coordination
 - Sync with DevEx for project scaffolding and build pipelines.
 - Partner with Docs Guild to translate UX decisions into operator guides.