feat(perf): 帧率采样汇总纯函数 + 测试（P21）

- PerformanceSummary.summarize：丢弃 warmup 后求每秒 FPS 的均值/最低/最高，
  空样本返回 None；含 3 条单测（TDD）。

2 files changed, 35 insertions, 0 deletions

diff --git a/src/LivingVillage.Desktop.Tests/LivingVillage.Desktop.Tests.fsproj b/src/LivingVillage.Desktop.Tests/LivingVillage.Desktop.Tests.fsproj
index 87e9e9d..a0c98b0 100644
--- a/src/LivingVillage.Desktop.Tests/LivingVillage.Desktop.Tests.fsproj
+++ b/src/LivingVillage.Desktop.Tests/LivingVillage.Desktop.Tests.fsproj
@@ -12,6 +12,7 @@
     <Compile Include="P16UiTests.fs" />
     <Compile Include="PrototypeTests.fs" />
     <Compile Include="MapGenTests.fs" />
+    <Compile Include="PerformanceSummaryTests.fs" />
     <Compile Include="M3BatchOutputTests.fs" />
     <Compile Include="SampleTests.fs" />
   </ItemGroup>
diff --git a/src/LivingVillage.Desktop.Tests/PerformanceSummaryTests.fs b/src/LivingVillage.Desktop.Tests/PerformanceSummaryTests.fs
new file mode 100644
index 0000000..cd7c3b1
--- /dev/null
+++ b/src/LivingVillage.Desktop.Tests/PerformanceSummaryTests.fs
@@ -0,0 +1,34 @@
+namespace LivingVillage.Desktop.Tests
+
+open System
+open Microsoft.VisualStudio.TestTools.UnitTesting
+open LivingVillage.Desktop
+
+[<TestClass>]
+type PerformanceSummaryTests () =
+
+    let close (expected: float) (actual: float) =
+        Assert.IsTrue(abs (expected - actual) < 0.0001, sprintf "expected %f but got %f" expected actual)
+
+    [<TestMethod>]
+    member _.SummarizeDropsWarmupAndReportsMeanMinMax () =
+        match PerformanceSummary.summarize 2 [ 10.0; 20.0; 30.0; 40.0 ] with
+        | None -> Assert.Fail("expected a summary")
+        | Some summary ->
+            Assert.AreEqual<int>(2, summary.Count)
+            close 35.0 summary.Mean
+            close 30.0 summary.Min
+            close 40.0 summary.Max
+
+    [<TestMethod>]
+    member _.SummarizeReturnsNoneWhenNoRealSampleRemains () =
+        Assert.IsTrue((PerformanceSummary.summarize 5 [ 1.0; 2.0 ]).IsNone)
+        Assert.IsTrue((PerformanceSummary.summarize 0 []).IsNone)
+
+    [<TestMethod>]
+    member _.SummarizeWithZeroWarmupKeepsEverySample () =
+        match PerformanceSummary.summarize 0 [ 60.0; 59.5; 61.0 ] with
+        | None -> Assert.Fail("expected a summary")
+        | Some summary ->
+            Assert.AreEqual<int>(3, summary.Count)
+            close 59.5 summary.Min