fix: Thread→coroutine, PlacementGuideView 메인스레드 보장

- #2: PiezoMonitoringView raw Thread → measureScope.launch + Dispatchers.Default
  withContext(Main)으로 state 변경 보장, composable 떠나면 자동 취소
- #22: PlacementGuideView onMultiChannelComplete 콜백 → handler.post 감싸기
  BLE Binder 스레드에서 Compose state 직접 변경 → 메인 스레드 보장
- nested handler.post 제거, throttle 시 직접 state 리셋

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

app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PiezoMonitoringView.kt

@@ -106,6 +106,8 @@ fun PiezoMonitoringView(appState: AppState) {
         return sorted.subList(1, sorted.size - 1).average()
     }
 
+    val measureScope = rememberCoroutineScope()
+
     fun measure() {
         if (isMeasuring) {
             Log.w("PiezoMonitor", "measure() called while already measuring — SKIPPED")
@@ -129,11 +131,12 @@ fun PiezoMonitoringView(appState: AppState) {
         bleManager.piezoCollector.onMultiChannelComplete = { channels ->
             Log.d("PiezoMonitor", "RECEIVED ${channels.size} channels: ${channels.map { "CH${it.channel}(${it.buffer.size})" }}")
             // 분석을 백그라운드에서 수행 후 UI 업데이트는 메인 스레드로
-            Thread {
+            measureScope.launch {
+            kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Default) {
                 val analysisStart = System.currentTimeMillis()
                 // channels를 로컬 복사 (Thread safety)
                 val channelsCopy = channels.toList()
-                handler.post {
+                kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Main) {
                     lastMultiChannelResult.clear()
                     lastMultiChannelResult.addAll(channelsCopy)
                 }
@@ -303,14 +306,17 @@ fun PiezoMonitoringView(appState: AppState) {
                 }
 
                 // allWalls를 UI state에 저장 (ChannelPanel에서 사용)
-                handler.post { lastAllWalls = allWalls.toList() }
+                val wallsCopy = allWalls.toList()
+                kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Main) {
+                    lastAllWalls = wallsCopy
+                }
                 val finalRawVol = rawVolumeMl
                 val finalTotalWalls = totalWallCount
                 val analysisMs = System.currentTimeMillis() - analysisStart
                 Log.d("PiezoMonitor", "Analysis took ${analysisMs}ms")
 
                 // UI 업데이트는 메인 스레드에서
-                handler.post {
+                kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Main) {
                     if (finalRawVol != null && finalRawVol > 0) {
                         if (isAutoMeasuring) {
                             if (allChannelsReceived) {
@@ -346,16 +352,14 @@ fun PiezoMonitoringView(appState: AppState) {
                     measureRetryCount = 0
                     try { measureDoneSignal.value.complete(Unit) } catch (_: Exception) {}
                 }
-            }.start()
+            } }
         }
         bleManager.piezoCollector.onLog = { msg -> Log.d("PiezoCollector", msg) }
 
         if (!bleManager.sendChannelsOnly()) {
             // Throttle됨 — isMeasuring 리셋 (deadlock 방지)
-            handler.post {
-                isMeasuring = false
-                try { measureDoneSignal.value.complete(Unit) } catch (_: Exception) {}
-            }
+            isMeasuring = false
+            try { measureDoneSignal.value.complete(Unit) } catch (_: Exception) {}
             return
         }
 

app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PlacementGuideView.kt

@@ -525,6 +525,8 @@ fun PlacementGuideView(appState: AppState) {
 
             fun sendMeasureCommand() {
                 bleManager.piezoCollector.onMultiChannelComplete = { channels ->
+                    // 메인 스레드에서 처리 (BLE 콜백은 Binder 스레드)
+                    handler.post {
                     isScanning = false
                     scanCount++
 
@@ -682,6 +684,7 @@ fun PlacementGuideView(appState: AppState) {
                         direction = directionHint
                     )
                 }
+                } // handler.post
                 bleManager.piezoCollector.onLog = { msg -> Log.d("PlacementGuide", msg) }
                 if (!bleManager.sendAllChannels()) {
                     // Throttle됨 — isScanning 리셋 (deadlock 방지)