Add unit tests for Router configuration and transport layers

- Implemented tests for RouterConfig, RoutingOptions, StaticInstanceConfig, and RouterConfigOptions to ensure default values are set correctly.
- Added tests for RouterConfigProvider to validate configurations and ensure defaults are returned when no file is specified.
- Created tests for ConfigValidationResult to check success and error scenarios.
- Developed tests for ServiceCollectionExtensions to verify service registration for RouterConfig.
- Introduced UdpTransportTests to validate serialization, connection, request-response, and error handling in UDP transport.
- Added scripts for signing authority gaps and hashing DevPortal SDK snippets.

docs/modules/export-center/devportal-offline-manifest.md

@@ -58,6 +58,7 @@ devportal-offline/
 - Export Center expects `manifest.json` at bundle root; validates sha256/bytes before publishing.
 - Offline bundle must build via `npm run build:offline` without network calls after initial `npm ci` + `npm run sync:spec`.
 - Specs and SDK archives are treated as opaque; manifest carries their hashes for downstream verification.
+- Record all hashes in `src/DevPortal/StellaOps.DevPortal.Site/SHA256SUMS.devportal-stubs` (or final SHA file) to keep determinism visible to docs/implplan sprints.
 
 ## Open items
 - Add per-language SDK metadata (version, commit SHA) once SDKREL-64-002 finalises.