feat(alignment): 센서 detach 시 주황 경고 팝업 — 텍스트 변경만으로 사용자가 놓치던 문제

- DetachmentDetection.isDetached 가 true 가 되는 rising edge 에 Dialog 팝업
- wakeup 알람과 동일한 주황(Material 500) 톤 + Warning 아이콘
- 재부착 시 팝업 자동 dismiss (사용자 확인 부담 ↓)
- 기존 directionHint / LED mode 4 / phase reset 동작은 그대로 유지

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -161,6 +161,10 @@ fun PlacementGuideView(appState: AppState) {
         onDispose { bleManager.sendLedMode(0) }
     }
 
+    // Detachment alert (rising edge → 팝업, 재부착 시 자동 해제)
+    var showDetachAlert by remember { mutableStateOf(false) }
+    var prevDetached by remember { mutableStateOf(false) }
+
     val detectedCount = channelDetected.count { it }
 
     val isGreenZone = isLocked || placementScore >= 70
@@ -176,6 +180,53 @@ fun PlacementGuideView(appState: AppState) {
         1f to MlPrimary.copy(alpha = 0.10f)
     )
 
+    // 센서 분리 알림 (주황 warning) — wakeup 알람과 동일 패턴
+    if (showDetachAlert) {
+        androidx.compose.ui.window.Dialog(
+            onDismissRequest = { },
+            properties = androidx.compose.ui.window.DialogProperties(
+                dismissOnBackPress = false, dismissOnClickOutside = false
+            )
+        ) {
+            Box(
+                modifier = Modifier
+                    .fillMaxWidth(0.92f)
+                    .clip(RoundedCornerShape(24.dp))
+                    .background(Color(0xFFFF9800))   // Material Orange 500
+                    .padding(horizontal = 28.dp, vertical = 36.dp),
+                contentAlignment = Alignment.Center
+            ) {
+                Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                    Icon(Icons.Default.Warning, contentDescription = null,
+                        tint = Color.White, modifier = Modifier.size(56.dp))
+                    Spacer(modifier = Modifier.height(12.dp))
+                    Text("센서가 분리되었습니다", fontSize = 26.sp,
+                        fontWeight = FontWeight.ExtraBold, color = Color.White,
+                        textAlign = TextAlign.Center)
+                    Spacer(modifier = Modifier.height(6.dp))
+                    Text("Sensor detached", fontSize = 16.sp,
+                        fontWeight = FontWeight.Medium, color = Color.White.copy(alpha = 0.9f),
+                        textAlign = TextAlign.Center)
+                    Spacer(modifier = Modifier.height(8.dp))
+                    Text("치골 위쪽에 다시 위치시켜 주세요",
+                        fontSize = 14.sp, color = Color.White.copy(alpha = 0.85f),
+                        textAlign = TextAlign.Center)
+                    Spacer(modifier = Modifier.height(24.dp))
+                    Button(
+                        onClick = { showDetachAlert = false },
+                        colors = ButtonDefaults.buttonColors(
+                            containerColor = Color.White, contentColor = Color(0xFFFF9800)
+                        ),
+                        modifier = Modifier.fillMaxWidth().height(56.dp),
+                        shape = RoundedCornerShape(14.dp)
+                    ) {
+                        Text("확인", fontSize = 20.sp, fontWeight = FontWeight.Bold)
+                    }
+                }
+            }
+        }
+    }
+
     Column(
         modifier = Modifier
             .fillMaxSize()
@@ -756,6 +807,10 @@ fun PlacementGuideView(appState: AppState) {
                     val fullCh = channels.filter { it.buffer.size >= 20 }
                     val buffers = channels.sortedBy { it.channel }.map { it.buffer }
                     val detachResult = if (fullCh.size >= 6) DetachmentDetection.detect(buffers) else null
+                    val nowDetached = detachResult?.isDetached == true
+                    if (nowDetached && !prevDetached) showDetachAlert = true       // rising edge → 팝업
+                    if (!nowDetached && prevDetached) showDetachAlert = false      // 재부착 → 자동 dismiss
+                    prevDetached = nowDetached
 
                     if (detachResult != null && detachResult.isDetached) {
                         directionHint = "Sensor detached. Restart above pubic bone."