Add signal contracts for reachability, exploitability, trust, and unknown symbols

- Introduced `ReachabilityState`, `RuntimeHit`, `ExploitabilitySignal`, `ReachabilitySignal`, `SignalEnvelope`, `SignalType`, `TrustSignal`, and `UnknownSymbolSignal` records to define various signal types and their properties.
- Implemented JSON serialization attributes for proper data interchange.
- Created project files for the new signal contracts library and corresponding test projects.
- Added deterministic test fixtures for micro-interaction testing.
- Included cryptographic keys for secure operations with cosign.

src/__Libraries/StellaOps.Router.Config/PayloadLimits.cs

@@ -0,0 +1,25 @@
+namespace StellaOps.Router.Config;
+
+/// <summary>
+/// Configuration for payload and memory limits.
+/// </summary>
+public sealed class PayloadLimits
+{
+    /// <summary>
+    /// Gets or sets the maximum request bytes per call.
+    /// Default: 10 MB.
+    /// </summary>
+    public long MaxRequestBytesPerCall { get; set; } = 10 * 1024 * 1024;
+
+    /// <summary>
+    /// Gets or sets the maximum request bytes per connection.
+    /// Default: 100 MB.
+    /// </summary>
+    public long MaxRequestBytesPerConnection { get; set; } = 100 * 1024 * 1024;
+
+    /// <summary>
+    /// Gets or sets the maximum aggregate in-flight bytes across all requests.
+    /// Default: 1 GB.
+    /// </summary>
+    public long MaxAggregateInflightBytes { get; set; } = 1024 * 1024 * 1024;
+}

src/__Libraries/StellaOps.Router.Config/RouterConfig.cs

@@ -0,0 +1,17 @@
+namespace StellaOps.Router.Config;
+
+/// <summary>
+/// Root configuration for the router.
+/// </summary>
+public sealed class RouterConfig
+{
+    /// <summary>
+    /// Gets or sets the payload limits configuration.
+    /// </summary>
+    public PayloadLimits PayloadLimits { get; set; } = new();
+
+    /// <summary>
+    /// Gets or sets the service configurations.
+    /// </summary>
+    public List<ServiceConfig> Services { get; set; } = [];
+}

src/__Libraries/StellaOps.Router.Config/ServiceConfig.cs

@@ -0,0 +1,60 @@
+using StellaOps.Router.Common;
+
+namespace StellaOps.Router.Config;
+
+/// <summary>
+/// Configuration for a service in the router.
+/// </summary>
+public sealed class ServiceConfig
+{
+    /// <summary>
+    /// Gets or sets the service name.
+    /// </summary>
+    public required string ServiceName { get; set; }
+
+    /// <summary>
+    /// Gets or sets the default version for requests without explicit version.
+    /// </summary>
+    public string? DefaultVersion { get; set; }
+
+    /// <summary>
+    /// Gets or sets the default transport type for this service.
+    /// </summary>
+    public TransportType DefaultTransport { get; set; } = TransportType.Tcp;
+
+    /// <summary>
+    /// Gets or sets the endpoint configurations.
+    /// </summary>
+    public List<EndpointConfig> Endpoints { get; set; } = [];
+}
+
+/// <summary>
+/// Configuration for an endpoint in a service.
+/// </summary>
+public sealed class EndpointConfig
+{
+    /// <summary>
+    /// Gets or sets the HTTP method.
+    /// </summary>
+    public required string Method { get; set; }
+
+    /// <summary>
+    /// Gets or sets the path template.
+    /// </summary>
+    public required string Path { get; set; }
+
+    /// <summary>
+    /// Gets or sets the default timeout.
+    /// </summary>
+    public TimeSpan? DefaultTimeout { get; set; }
+
+    /// <summary>
+    /// Gets or sets whether streaming is supported.
+    /// </summary>
+    public bool SupportsStreaming { get; set; }
+
+    /// <summary>
+    /// Gets or sets the claim requirements.
+    /// </summary>
+    public List<ClaimRequirement> RequiringClaims { get; set; } = [];
+}

src/__Libraries/StellaOps.Router.Config/StellaOps.Router.Config.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <LangVersion>preview</LangVersion>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\StellaOps.Router.Common\StellaOps.Router.Common.csproj" />
+  </ItemGroup>
+</Project>