feat: 右上角添加软急停滑块（平行四边形风格）

新增 EmergencyStopSlider 组件，水平滑到右侧触发软急停指令，
滑到左侧仅 UI 复位，等待机器人状态上报自动归位。非拖动时
跟随 motionState 状态同步滑块位置。

ControlCommands 新增 softEmergencyStop() 便捷函数。

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

AGENTS.md

@@ -212,6 +212,7 @@ gradlew installDebug
 - [x] 连接按钮交互优化：`CONNECTING` 状态下点击连接按钮仅断开回到 `DISCONNECTED`，不再自动重连，由用户手动再次点击发起重试
 - [x] 状态机补充：`RobotConnection` 允许 `CONNECTING → TIMEOUT` 合法转换
 - [x] 心跳启动时机修复：`ProtocolClient.connect()` 立即启动心跳线程，不再等待首次收到数据包后才启动；心跳在 `CONNECTING` 和 `CONNECTED` 状态下均正常运行
+- [x] 软急停滑块：右上角新增平行四边形水平滑块，滑到右侧触发软急停（`MOTION_DAMPING`），跟随机器人状态上报自动归位
 
 ### 待办
 

app/src/main/java/com/example/m20_gamepad/network/models/ControlCommands.kt

@@ -107,6 +107,9 @@ object ControlCommands {
         put("Charge", JsonPrimitive(charge))
     }
 
+    // ---- 2.8b 软急停 ----
+    fun softEmergencyStop(time: String = now()): String = motionControl(MOTION_DAMPING, time)
+
     // ---- 2.9 休眠模式设置 ----
     fun sleepSettings(sleep: Boolean, auto: Boolean, timeMinutes: Int, time: String = now()): String = buildAsdu(
         type = 1101, command = 6, time = time

app/src/main/java/com/example/m20_gamepad/ui/MainScreen.kt

@@ -3,6 +3,7 @@ package com.example.m20_gamepad.ui
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.BorderStroke
+import androidx.compose.foundation.gestures.detectHorizontalDragGestures
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -13,6 +14,7 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.navigationBars
+import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
@@ -43,8 +45,10 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.Outline
 import androidx.compose.ui.graphics.Path
 import androidx.compose.ui.graphics.Shape
+import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
@@ -218,7 +222,7 @@ fun MainScreen(
             )
         }
 
-        // ---- 右上角控制区：照明 + 休眠 + 充电 ----
+        // ---- 右上角控制区：软急停滑块 + 照明 + 休眠 + 充电 ----
         Column(
             modifier = Modifier
                 .align(Alignment.TopEnd)
@@ -226,6 +230,12 @@ fun MainScreen(
             horizontalAlignment = Alignment.End,
             verticalArrangement = Arrangement.spacedBy(6.dp)
         ) {
+            // 软急停滑块
+            EmergencyStopSlider(
+                isEmergencyStop = motionState == ControlCommands.MOTION_DAMPING,
+                connected = connectionState == ProtocolClient.State.CONNECTED,
+                onEmergencyStop = { viewModel.sendEmergencyStop() }
+            )
             // 照明：前灯+后灯，无缝隙
             val frontOn = ledStatus?.front == 1
             val backOn = ledStatus?.back == 1
@@ -696,6 +706,110 @@ private fun ChargeToggleButton(
     }
 }
 
+// ==================== 软急停滑块 ====================
+
+/**
+ * 水平滑块，平行四边形风格。用于触发软急停。
+ *
+ * 滑到右侧 → 发送软急停指令；滑到左侧 → 仅 UI 复位，不发指令。
+ * 机器人收到软急停后 3 秒自动切回空闲，状态上报会驱动滑块自动归位。
+ *
+ * @param isEmergencyStop 当前是否处于软急停状态（motionState == MOTION_DAMPING）
+ * @param connected 是否已连接（未连接时禁用交互）
+ * @param onEmergencyStop 滑块滑到右侧触发
+ */
+@Composable
+private fun EmergencyStopSlider(
+    isEmergencyStop: Boolean,
+    connected: Boolean,
+    onEmergencyStop: () -> Unit,
+    modifier: Modifier = Modifier
+) {
+    val sliderWidth = 150.dp
+    val sliderHeight = 32.dp
+    val thumbSize = 28.dp
+
+    // 0f = 左侧（正常），1f = 右侧（急停触发）
+    var fraction by remember { mutableStateOf(if (isEmergencyStop) 1f else 0f) }
+    var isDragging by remember { mutableStateOf(false) }
+
+    // 非拖动时跟随外部状态回调
+    LaunchedEffect(isEmergencyStop) {
+        if (!isDragging) {
+            fraction = if (isEmergencyStop) 1f else 0f
+        }
+    }
+
+    // 拖动结束后吸附：滑到右侧触发急停，滑到左侧仅复位 UI
+    fun snapAndFire() {
+        isDragging = false
+        if (fraction > 0.5f) {
+            fraction = 1f
+            onEmergencyStop()
+        } else {
+            fraction = 0f
+            // 不发送复位指令，等机器人状态上报自动同步
+        }
+    }
+
+    // 滑轨：遵循其他按钮的 containerColor 逻辑
+    val trackColor = if (connected) Color(0x66333333) else Color(0x33222222)
+    // 拇指：75% 红色
+    val thumbColor = Color(0xBFFF4444)
+    val skew = 3.dp
+
+    Box(
+        modifier = modifier
+            .width(sliderWidth)
+            .height(sliderHeight)
+    ) {
+        // 滑轨 — 平行四边形外框
+        Surface(
+            modifier = Modifier
+                .fillMaxSize(),
+            shape = ParallelogramShape(skewDp = skew, skewLeft = false),
+            color = trackColor
+        ) {}
+
+        // 文字显示在滑轨上
+        Text(
+            text = "急停",
+            modifier = Modifier.align(Alignment.Center),
+            color = Color(0xAAFFFFFF),
+            fontSize = 12.sp,
+            fontWeight = FontWeight.Medium
+        )
+
+        // 滑块拇指
+        val maxOffsetDp = sliderWidth - thumbSize
+        val density = LocalDensity.current
+        val maxOffsetPx = with(density) { maxOffsetDp.toPx() }
+        val thumbOffset = maxOffsetDp * fraction
+        // fraction=0 → offset=0 (左侧)
+        // fraction=1 → offset=maxOffsetDp (右侧)
+
+        Surface(
+            modifier = Modifier
+                .size(thumbSize, sliderHeight)
+                .offset(x = thumbOffset)
+                .pointerInput(connected) {
+                    if (!connected) return@pointerInput
+                    detectHorizontalDragGestures(
+                        onDragStart = { isDragging = true },
+                        onDragEnd = { snapAndFire() },
+                        onDragCancel = { snapAndFire() },
+                        onHorizontalDrag = { change, dragAmount ->
+                            change.consume()
+                            fraction = (fraction + dragAmount / maxOffsetPx).coerceIn(0f, 1f)
+                        }
+                    )
+                },
+            shape = ParallelogramShape(skewDp = skew, skewLeft = false),
+            color = thumbColor
+        ) {}
+    }
+}
+
 // ==================== 辅助函数 ====================
 
 private fun motionStateText(state: Int): String = when (state) {

app/src/main/java/com/example/m20_gamepad/ui/MainViewModel.kt

@@ -292,6 +292,15 @@ class MainViewModel(
         client?.sendCommandBlocking(ControlCommands.chargeControl(charge))
     }
 
+    /** 软急停：进入关节阻尼状态。 */
+    fun sendEmergencyStop() {
+        if (robot.canSendMotionControl) {
+            client?.sendCommandBlocking(ControlCommands.softEmergencyStop())
+        } else {
+            _actionFeedback.value = "未连接，无法发送软急停"
+        }
+    }
+
     fun sendSleepSettings(sleep: Boolean, auto: Boolean = false, timeMinutes: Int = 5) {
         client?.sendCommandBlocking(
             ControlCommands.sleepSettings(sleep, auto, timeMinutes)