feat(metrics): Add new histograms for chunk latency, results, and sources in AdvisoryAiMetrics

feat(telemetry): Record chunk latency, result count, and source count in AdvisoryAiTelemetry

fix(endpoint): Include telemetry source count in advisory chunks endpoint response

test(metrics): Enhance WebServiceEndpointsTests to validate new metrics for chunk latency, results, and sources

refactor(tests): Update test utilities for Deno language analyzer tests

chore(tests): Add performance tests for AdvisoryGuardrail with scenarios and blocked phrases

docs: Archive Sprint 137 design document for scanner and surface enhancements

src/Concelier/__Tests/StellaOps.Concelier.WebService.Tests/WebServiceEndpointsTests.cs

@@ -531,7 +531,14 @@ public sealed class WebServiceEndpointsTests : IAsyncLifetime
 
         var metrics = await CaptureMetricsAsync(
             AdvisoryAiMetrics.MeterName,
-            new[] { "advisory_ai_chunk_requests_total", "advisory_ai_chunk_cache_hits_total" },
+            new[]
+            {
+                "advisory_ai_chunk_requests_total",
+                "advisory_ai_chunk_cache_hits_total",
+                "advisory_ai_chunk_latency_milliseconds",
+                "advisory_ai_chunk_segments",
+                "advisory_ai_chunk_sources"
+            },
             async () =>
             {
                 const string url = "/advisories/CVE-2025-0001/chunks?tenant=tenant-a";
@@ -556,6 +563,17 @@ public sealed class WebServiceEndpointsTests : IAsyncLifetime
         var cacheHit = Assert.Single(cacheHitMeasurements!);
         Assert.Equal(1, cacheHit.Value);
         Assert.Equal("hit", GetTagValue(cacheHit, "result"));
+
+        Assert.True(metrics.TryGetValue("advisory_ai_chunk_latency_milliseconds", out var latencyMeasurements));
+        Assert.Equal(2, latencyMeasurements!.Count);
+        Assert.All(latencyMeasurements!, measurement => Assert.True(measurement.Value > 0));
+
+        Assert.True(metrics.TryGetValue("advisory_ai_chunk_segments", out var segmentMeasurements));
+        Assert.Equal(2, segmentMeasurements!.Count);
+        Assert.Contains(segmentMeasurements!, measurement => GetTagValue(measurement, "truncated") == "false");
+
+        Assert.True(metrics.TryGetValue("advisory_ai_chunk_sources", out var sourceMeasurements));
+        Assert.Equal(2, sourceMeasurements!.Count);
     }
 
     [Fact]
@@ -2161,7 +2179,7 @@ public sealed class WebServiceEndpointsTests : IAsyncLifetime
             }
         };
 
-        listener.SetMeasurementEventCallback<long>((instrument, measurement, tags, state) =>
+        void RecordMeasurement(Instrument instrument, double measurement, ReadOnlySpan<KeyValuePair<string, object?>> tags)
         {
             if (!measurementMap.TryGetValue(instrument.Name, out var list))
             {
@@ -2175,7 +2193,13 @@ public sealed class WebServiceEndpointsTests : IAsyncLifetime
             }
 
             list.Add(new MetricMeasurement(instrument.Name, measurement, tagDictionary));
-        });
+        }
+
+        listener.SetMeasurementEventCallback<long>((instrument, measurement, tags, state)
+            => RecordMeasurement(instrument, measurement, tags));
+
+        listener.SetMeasurementEventCallback<double>((instrument, measurement, tags, state)
+            => RecordMeasurement(instrument, measurement, tags));
 
         listener.Start();
         try
@@ -2239,7 +2263,7 @@ public sealed class WebServiceEndpointsTests : IAsyncLifetime
         return new JwtSecurityTokenHandler().WriteToken(token);
     }
 
-    private sealed record MetricMeasurement(string Instrument, long Value, IReadOnlyDictionary<string, object?> Tags);
+    private sealed record MetricMeasurement(string Instrument, double Value, IReadOnlyDictionary<string, object?> Tags);
 
     private sealed class DemoJob : IJob
     {