feat(telemetry): add telemetry client and services for tracking events

- Implemented TelemetryClient to handle event queuing and flushing to the telemetry endpoint.
- Created TtfsTelemetryService for emitting specific telemetry events related to TTFS.
- Added tests for TelemetryClient to ensure event queuing and flushing functionality.
- Introduced models for reachability drift detection, including DriftResult and DriftedSink.
- Developed DriftApiService for interacting with the drift detection API.
- Updated FirstSignalCardComponent to emit telemetry events on signal appearance.
- Enhanced localization support for first signal component with i18n strings.

src/Signer/StellaOps.Signer/StellaOps.Signer.Core/PredicateTypes.cs

@@ -43,6 +43,13 @@ public static class PredicateTypes
     /// </summary>
     public const string StellaOpsPolicy = "stella.ops/policy@v1";
 
+    /// <summary>
+    /// StellaOps Policy Decision attestation predicate type.
+    /// Sprint: SPRINT_3801_0001_0001_policy_decision_attestation
+    /// Captures policy gate results with references to input evidence (SBOM, VEX, RichGraph).
+    /// </summary>
+    public const string StellaOpsPolicyDecision = "stella.ops/policy-decision@v1";
+
     /// <summary>
     /// StellaOps Evidence chain predicate type.
     /// </summary>
@@ -60,6 +67,13 @@ public static class PredicateTypes
     /// </summary>
     public const string StellaOpsGraph = "stella.ops/graph@v1";
 
+    /// <summary>
+    /// StellaOps Reachability Witness predicate type for DSSE attestations.
+    /// Sprint: SPRINT_3620_0001_0001_reachability_witness_dsse
+    /// Cryptographic proof that specific reachability analysis was performed.
+    /// </summary>
+    public const string StellaOpsReachabilityWitness = "stella.ops/reachabilityWitness@v1";
+
     /// <summary>
     /// CycloneDX SBOM predicate type.
     /// </summary>
@@ -108,7 +122,8 @@ public static class PredicateTypes
     {
         return predicateType == StellaOpsGraph
             || predicateType == StellaOpsReplay
-            || predicateType == StellaOpsEvidence;
+            || predicateType == StellaOpsEvidence
+            || predicateType == StellaOpsReachabilityWitness;
     }
 
     /// <summary>
@@ -127,9 +142,11 @@ public static class PredicateTypes
             StellaOpsVex,
             StellaOpsReplay,
             StellaOpsPolicy,
+            StellaOpsPolicyDecision,
             StellaOpsEvidence,
             StellaOpsVexDecision,
             StellaOpsGraph,
+            StellaOpsReachabilityWitness,
             // Third-party types
             CycloneDxSbom,
             SpdxSbom,