fix: strip trailing recorder-stop noise in PlayerEngine (#14)

box-v7 패턴: alt+tab → click(PowerShell) → ctrl+c ctrl+c 가 재생 시
SUT 외부 창(브라우저 등)에 입력을 보내는 버그.

- PlayerEngine.Run: trailing (alt+tab → optional click → ctrl+c+) 감지 시 제거
- leading alt+tab 제거와 대칭적으로 동작
- ctrl+c 단독으로는 제거하지 않음 (SUT 내 복사 액션과 구분)
- 테스트 2건 추가 (138 total)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/Recordingtest.Player.Tests/PlayerEngineTests.cs

@@ -221,6 +221,58 @@ steps:
         Assert.Equal(StepKind.Focus, s.Steps[1].Kind);
     }
 
+    // ---- trailing recorder-stop noise stripping --------------------------------
+
+    [Fact]
+    public void TrailingRecorderStop_AltTabClickCtrlC_Stripped()
+    {
+        // box-v7 pattern: real work → alt+tab → click → ctrl+c ctrl+c
+        var host = new FakePlayerHost();
+        var engine = new PlayerEngine(new PlayerEngineOptions { PreserveTiming = false });
+        var scenario = new Scenario
+        {
+            Steps =
+            {
+                new Step { Kind = StepKind.Type, Value = "BOX" },          // real work
+                new Step { Kind = StepKind.Hotkey, Value = "enter" },       // real work
+                new Step { Kind = StepKind.Hotkey, Value = "alt+tab" },     // recorder stop →
+                new Step { Kind = StepKind.Click, RawCoord = [771, 833] }, // click terminal
+                new Step { Kind = StepKind.Hotkey, Value = "ctrl+c" },     // stop recorder
+                new Step { Kind = StepKind.Hotkey, Value = "ctrl+c" },     // stop recorder
+            },
+        };
+
+        engine.Run(scenario, host);
+
+        // Only the two real-work steps should have fired — no Clicks, hotkey only "enter"
+        Assert.Empty(host.Clicks);                         // click (771,833) stripped
+        Assert.Single(host.Types);                         // only "BOX"
+        Assert.Equal("BOX", host.Types[0]);
+        Assert.Single(host.Hotkeys);                       // only "enter", not ctrl+c
+        Assert.Equal("enter", host.Hotkeys[0]);
+    }
+
+    [Fact]
+    public void TrailingCtrlCAlone_NotStripped_RequiresAltTab()
+    {
+        // ctrl+c without preceding alt+tab is a legitimate SUT action (copy)
+        var host = new FakePlayerHost();
+        var engine = new PlayerEngine(new PlayerEngineOptions { PreserveTiming = false });
+        var scenario = new Scenario
+        {
+            Steps =
+            {
+                new Step { Kind = StepKind.Type,   Value = "BOX" },
+                new Step { Kind = StepKind.Hotkey, Value = "ctrl+c" },
+            },
+        };
+
+        engine.Run(scenario, host);
+        // ctrl+c alone at the end must NOT be stripped (it's a copy action)
+        Assert.Single(host.Hotkeys);
+        Assert.Equal("ctrl+c", host.Hotkeys[0]);
+    }
+
     private static string LocateEngineSource([CallerFilePath] string here = "")
     {
         // here = .../tests/Recordingtest.Player.Tests/PlayerEngineTests.cs