feat: 状态栏优化 — 背景吸附+连接按钮合并+隐藏系统状态栏

- StatusBar 重构为 Box + Row 双层结构，背景延伸到屏幕顶端
- 连接按钮合并到顶部 ConnectionIndicator，删除底部独立连接按钮
- ConnectionIndicator 改为按钮形态（Surface + 圆角边框）
- 隐藏系统状态栏（WindowInsetsControllerCompat），压缩 StatusBar 高度

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

app/src/main/java/com/example/m20_gamepad/MainActivity.kt

@@ -6,6 +6,8 @@ import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.platform.LocalContext
+import androidx.core.view.WindowInsetsCompat
+import androidx.core.view.WindowInsetsControllerCompat
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.rememberNavController
@@ -18,6 +20,11 @@ class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
+        // 隐藏系统状态栏，顶部区域完全由自定义 StatusBar 接管
+        WindowInsetsControllerCompat(window, window.decorView).apply {
+            hide(WindowInsetsCompat.Type.statusBars())
+            systemBarsBehavior = WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
+        }
         setContent {
             M20_gamepadTheme {
                 AppNavGraph()

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

@@ -2,6 +2,7 @@ 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.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -14,7 +15,6 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.navigationBars
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
-import androidx.compose.foundation.layout.statusBars
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.layout.windowInsetsPadding
 import androidx.compose.foundation.rememberScrollState
@@ -134,9 +134,14 @@ fun MainScreen(
             wifiSignalLevel = wifiSignalLevel,
             onStatusClick = { statusPanelVisible = true },
             onSettingsClick = onSettingsClick,
-            modifier = Modifier
-                .align(Alignment.TopCenter)
-                .windowInsetsPadding(WindowInsets.statusBars)
+            onConnectToggle = {
+                if (connectionState == ProtocolClient.State.CONNECTED) {
+                    viewModel.disconnect()
+                } else {
+                    viewModel.connect()
+                }
+            },
+            modifier = Modifier.align(Alignment.TopCenter)
         )
 
         // ---- 底部控制区 ----
@@ -180,19 +185,24 @@ private fun StatusBar(
     wifiSignalLevel: Int,
     onStatusClick: () -> Unit,
     onSettingsClick: () -> Unit,
+    onConnectToggle: () -> Unit,
     modifier: Modifier = Modifier
 ) {
-    Row(
+    Box(
         modifier = modifier
             .fillMaxWidth()
             .background(OverlayBg)
-            .padding(horizontal = 12.dp, vertical = 8.dp),
-        verticalAlignment = Alignment.CenterVertically,
-        horizontalArrangement = Arrangement.SpaceBetween
     ) {
+        Row(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(horizontal = 12.dp, vertical = 4.dp),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.SpaceBetween
+        ) {
         // 连接状态 + WiFi 信号 + Ping 延迟
         Row(verticalAlignment = Alignment.CenterVertically) {
-            ConnectionIndicator(connectionState)
+            ConnectionIndicator(connectionState, onConnectToggle)
             Spacer(Modifier.width(12.dp))
             WifiSignalIcon(level = wifiSignalLevel)
             Spacer(Modifier.width(12.dp))
@@ -231,10 +241,11 @@ private fun StatusBar(
             }
         }
     }
+    }
 }
 
 @Composable
-private fun ConnectionIndicator(state: ProtocolClient.State) {
+private fun ConnectionIndicator(state: ProtocolClient.State, onClick: () -> Unit) {
     val (color, text) = when (state) {
         ProtocolClient.State.CONNECTED -> Color(0xFF4CAF50) to "已连接"
         ProtocolClient.State.CONNECTING -> Color(0xFFFFC107) to "连接中"
@@ -242,14 +253,24 @@ private fun ConnectionIndicator(state: ProtocolClient.State) {
         ProtocolClient.State.ERROR -> Color(0xFFF44336) to "错误"
         ProtocolClient.State.DISCONNECTED -> Color(0xFF9E9E9E) to "未连接"
     }
-    Row(verticalAlignment = Alignment.CenterVertically) {
-        Box(
-            modifier = Modifier
-                .size(10.dp)
-                .background(color, CircleShape)
-        )
-        Spacer(Modifier.width(6.dp))
-        Text(text, color = OverlayText, fontSize = 14.sp)
+    Surface(
+        onClick = onClick,
+        shape = RoundedCornerShape(14.dp),
+        border = BorderStroke(1.dp, Color(0x55FFFFFF)),
+        color = Color(0x22000000)
+    ) {
+        Row(
+            modifier = Modifier.padding(horizontal = 10.dp, vertical = 2.dp),
+            verticalAlignment = Alignment.CenterVertically
+        ) {
+            Box(
+                modifier = Modifier
+                    .size(10.dp)
+                    .background(color, CircleShape)
+            )
+            Spacer(Modifier.width(6.dp))
+            Text(text, color = OverlayText, fontSize = 14.sp)
+        }
     }
 }
 
@@ -376,19 +397,6 @@ private fun ControlButtons(
             .verticalScroll(scrollState)
             .padding(top = 4.dp, bottom = 4.dp)
     ) {
-        // 连接/断开
-        Button(
-            onClick = {
-                if (connected) viewModel.disconnect() else viewModel.connect()
-            },
-            colors = ButtonDefaults.buttonColors(
-                containerColor = if (connected) Color(0xFFF44336) else Color(0xFF4CAF50)
-            ),
-            modifier = Modifier.width(110.dp)
-        ) {
-            Text(if (connected) "断开" else "连接")
-        }
-
         // 运动状态转换
         ControlButton(
             "起立",