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/api/SHA256SUMS

@@ -0,0 +1,3 @@
+# Hash index for exceptions API docs
+# <sha256>  <relative-path>
+ec33d6612473d997196ec463042cc5cff21e107ab9d267fd2fa4ffd166e6f25c  docs/api/exceptions.md

docs/api/exceptions.md

@@ -0,0 +1,12 @@
+# Exceptions API (stub)
+
+> Status: BLOCKED — awaiting exception API contract (DOCS-EXC-25-003).
+
+## To be provided
+- OpenAPI spec path (once delivered)
+- Endpoint list, payloads, errors, idempotency semantics
+- Deterministic examples (request/response NDJSON) with hashes
+
+## Determinism
+- When examples/spec arrive, hash into `docs/api/SHA256SUMS`.
+- Keep sample payloads under `docs/api/exceptions/samples/` (one file per case) with stable ordering/fields.