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.

tools/cosign/README.md

@@ -106,3 +106,19 @@ COSIGN_ALLOW_DEV_KEY=1 COSIGN_PASSWORD=stellaops-dev \
 2. `COSIGN_PRIVATE_KEY_B64` (decoded to temp file)
 3. `tools/cosign/cosign.key` (production drop-in)
 4. `tools/cosign/cosign.dev.key` (only if `COSIGN_ALLOW_DEV_KEY=1`)
+
+### sign-authority-gaps.sh
+Signs Authority gap artefacts (AU1–AU10, RR1–RR10) under `docs/modules/authority/gaps/artifacts/`.
+
+```
+# Production (Authority key via CI secret or cosign.key drop-in)
+OUT_DIR=docs/modules/authority/gaps/dsse/2025-12-04 tools/cosign/sign-authority-gaps.sh
+
+# Development (dev key, smoke only)
+COSIGN_ALLOW_DEV_KEY=1 COSIGN_PASSWORD=stellaops-dev \
+  OUT_DIR=docs/modules/authority/gaps/dev-smoke/2025-12-04 \
+  tools/cosign/sign-authority-gaps.sh
+```
+
+- Outputs bundles or dsse signatures plus `SHA256SUMS` in `OUT_DIR`.
+- tlog upload disabled (`--tlog-upload=false`) and prompts auto-accepted (`--yes`) for offline use.