test: surface path timing contracts in live harness

MinecraftClient.Tests/Pathing/Execution/PathExecutionLogObserverTests.cs

@@ -0,0 +1,39 @@
+using MinecraftClient.Mapping;
+using MinecraftClient.Pathing.Core;
+using MinecraftClient.Pathing.Execution;
+using MinecraftClient.Pathing.Execution.Telemetry;
+using Xunit;
+
+namespace MinecraftClient.Tests.Pathing.Execution;
+
+public sealed class PathExecutionLogObserverTests
+{
+    [Fact]
+    public void Observer_EmitsMachineReadablePathMetricLines()
+    {
+        List<string> lines = [];
+        PathExecutionLogObserver observer = new(lines.Add);
+        PathSegment segment = new()
+        {
+            Start = new Location(10, 64, 10),
+            End = new Location(11, 64, 10),
+            MoveType = MoveType.Traverse,
+            ExitTransition = PathTransitionType.ContinueStraight,
+        };
+
+        observer.OnNavigationStarted([segment]);
+        observer.OnSegmentStarted(0, 1, segment);
+        observer.OnSegmentCompleted(0, 1, segment, 7, new Location(11.5, 64, 10.5));
+        observer.OnReplanStarted(1, new Location(11.5, 64, 10.5));
+        observer.OnReplanSucceeded(1, [segment]);
+        observer.OnNavigationCompleted(7);
+
+        Assert.Collection(lines,
+            line => Assert.Equal("[PathMetric] routeStart segments=1", line),
+            line => Assert.Equal("[PathMetric] segmentStart index=0 total=1 move=Traverse transition=ContinueStraight", line),
+            line => Assert.Equal("[PathMetric] segmentComplete index=0 total=1 move=Traverse ticks=7 x=11.50 y=64.00 z=10.50", line),
+            line => Assert.Equal("[PathMetric] replanStart count=1 x=11.50 y=64.00 z=10.50", line),
+            line => Assert.Equal("[PathMetric] replanSuccess count=1 segments=1", line),
+            line => Assert.Equal("[PathMetric] routeComplete totalTicks=7", line));
+    }
+}