player: active foreground wait replaces fixed 600ms sleep (#14)

BringSutToForeground() now polls GetForegroundWindow() == SUT hwnd at 25ms
intervals up to 2s, followed by a 100ms tail settle, instead of the brittle
fixed 600ms sleep. First-attempt replay of box-v6.yaml is now reliable
(previously dropped the opening "BOX" keystrokes on a cold start).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

PLAN.md

@@ -10,9 +10,8 @@
 
 ## P1 — 라이브 검증 (사용자 환경 필요)
 
-4. **이슈 #14 재생 안정화** — 첫 시도 BOX 타이핑 누락 문제. foreground settle 600ms→능동 대기 전환 또는 첫 type 이전 `Keyboard.Type` warm-up. `/contract player-foreground-stabilize`.
-5. **recorder Gap I-1** — type 스텝 target을 `Automation.FocusedElement`로 직접 채워 null_target_steps=0 달성. `/contract recorder-focused-element-target`.
-6. **engine-bridge v3** — ReflectionEngineStateProvider 실매핑 (smoke test 이후)
+4. **recorder Gap I-1** — type 스텝 target을 `Automation.FocusedElement`로 직접 채워 null_target_steps=0 달성. Player fallback 의존도 줄이기.
+5. **engine-bridge v3** — ReflectionEngineStateProvider 실매핑 (smoke test 이후)
 
 ## Follow-ups (non-blocking)
 

PROGRESS.md

@@ -59,7 +59,7 @@ _(없음)_
 - [ ] player: `wait_for` UIA 이벤트 매핑 강화 (현재 host passthrough).
 - [ ] player: `UiaPlayerHost` uia_path resolver가 마지막 `@AutomationId`만 사용 — 전체 ancestor chain 지원 필요.
 - [ ] recorder: IME 조합 키 처리 (contract risks).
-- [ ] player: foreground settle이 경계선(600ms) — 1차 재생이 가끔 BOX 타이핑 누락. 능동 대기(focus-ready polling)로 전환 고려. (issue #14 후속)
+- [x] ~~player: foreground settle 안정화~~ — 능동 대기(`GetForegroundWindow` polling 2s + 100ms settle)로 전환, 1차 재생 성공 확인
 - [ ] recorder: null_target 이벤트 자체를 줄이기 — `Automation.FocusedElement` 직접 조회해 type 스텝 target 채우기 (issue #14 Gap I-1). 현재는 player fallback으로 우회.
 
 ## Blocked

src/Recordingtest.Player/UiaPlayerHost.cs

@@ -212,21 +212,34 @@ public sealed class UiaPlayerHost : IPlayerHost, IDisposable
     /// was launched from a shell that still has focus when the first Type/Hotkey
     /// step fires.
     /// </summary>
+    [System.Runtime.InteropServices.DllImport("user32.dll")]
+    private static extern IntPtr GetForegroundWindow();
+
     public void BringSutToForeground()
     {
         try
         {
             var w = _app?.GetMainWindow(_automation, TimeSpan.FromSeconds(5));
             if (w is null) return;
+            var targetHwnd = w.Properties.NativeWindowHandle.ValueOrDefault;
             try { w.SetForeground(); } catch { /* best-effort */ }
             try { w.Focus(); } catch { /* best-effort */ }
-            // Small settle so the OS-level focus switch takes effect before
-            // the first SendInput. 150ms is enough in practice on Win10.
-            // Increased from 150→600ms because FlaUI Keyboard.Type drops the
-            // first couple of characters if SendInput fires before the OS
-            // finishes the focus transition (observed: "BOX" lost on first
-            // step, "10" succeeded later once the app had settled).
-            System.Threading.Thread.Sleep(600);
+
+            // Issue #14 follow-up: active wait instead of fixed 600ms sleep.
+            // Poll until the OS reports the SUT as the foreground window, up
+            // to 2s. Previously a 600ms fixed sleep was threshold-sensitive
+            // and caused the first "BOX" keystroke to get dropped on a cold
+            // first run.
+            var deadline = DateTime.UtcNow.AddSeconds(2);
+            while (DateTime.UtcNow < deadline)
+            {
+                if (targetHwnd != IntPtr.Zero && GetForegroundWindow() == targetHwnd)
+                    break;
+                System.Threading.Thread.Sleep(25);
+            }
+            // Tiny additional settle for the OS keyboard-focus IPC to finish
+            // after the foreground transition is observed.
+            System.Threading.Thread.Sleep(100);
         }
         catch
         {