feat(chat): 思维链保留 10 分钟并自动折叠；输入栏下方留白承载忙碌提示

流式结束后把思维链挂到落库消息上，10 分钟后自动清除；ThinkingCard 在 active 变 false 时自动折叠，历史思维链默认折叠。输入栏底部预留 22dp 避开屏幕圆角，顶栏副标题只留连接状态，忙碌提示移到输入栏下方（带左缩进）。

app/src/main/kotlin/top/yeij/cyrene/ui/chat/ChatScreen.kt

@@ -3,11 +3,13 @@ package top.yeij.cyrene.ui.chat
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.imePadding
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.width
@@ -45,6 +47,9 @@ import top.yukonga.miuix.kmp.theme.MiuixTheme
 /** 判定「贴着底部」的容差（px）。 */
 private const val BOTTOM_TOLERANCE = 64
 
+/** 输入栏下方预留的高度：避开屏幕圆角，同时承载忙碌提示。 */
+private val InputBottomSpacer = 22.dp
+
 @Composable
 fun ChatScreen(
     container: AppContainer,
@@ -96,7 +101,7 @@ fun ChatScreen(
         topBar = {
             SmallTopAppBar(
                 title = "与昔涟",
-                subtitle = statusLabel(state),
+                subtitle = connectionLabel(state),
                 navigationIcon = {
                     IconButton(onClick = onOpenDrawer) {
                         Icon(imageVector = MiuixIcons.Basic.Sidebar, contentDescription = "菜单")
@@ -107,6 +112,7 @@ fun ChatScreen(
         bottomBar = {
             InputBar(
                 value = state.draft,
+                busyText = busyLabel(state),
                 onValueChange = viewModel::onDraftChange,
                 onSend = viewModel::send,
             )
@@ -172,30 +178,46 @@ fun ChatScreen(
 @Composable
 private fun InputBar(
     value: String,
+    busyText: String,
     onValueChange: (String) -> Unit,
     onSend: () -> Unit,
 ) {
-    Row(
+    Column(
         modifier = Modifier
             .fillMaxWidth()
             .imePadding()
-            .padding(horizontal = 12.dp, vertical = 8.dp),
-        verticalAlignment = Alignment.Bottom,
+            .padding(start = 12.dp, end = 12.dp, top = 8.dp, bottom = 4.dp),
     ) {
-        TextField(
-            value = value,
-            onValueChange = onValueChange,
-            label = "和昔涟说点什么…",
-            useLabelAsPlaceholder = true,
-            maxLines = 5,
-            modifier = Modifier.weight(1f),
-        )
-        Spacer(Modifier.width(8.dp))
-        Button(
-            onClick = onSend,
-            enabled = value.isNotBlank(),
+        Row(verticalAlignment = Alignment.Bottom) {
+            TextField(
+                value = value,
+                onValueChange = onValueChange,
+                label = "和昔涟说点什么…",
+                useLabelAsPlaceholder = true,
+                maxLines = 5,
+                modifier = Modifier.weight(1f),
+            )
+            Spacer(Modifier.width(8.dp))
+            Button(
+                onClick = onSend,
+                enabled = value.isNotBlank(),
+            ) {
+                Text("发送")
+            }
+        }
+        // 输入栏下方预留的空间：让输入框/按钮避开屏幕圆角，同时放忙碌提示
+        Box(
+            modifier = Modifier
+                .fillMaxWidth()
+                .height(InputBottomSpacer)
+                .padding(start = 12.dp, top = 4.dp),
+            contentAlignment = Alignment.CenterStart,
         ) {
-            Text("发送")
+            Text(
+                text = busyText,
+                style = MiuixTheme.textStyles.footnote2,
+                color = MiuixTheme.colorScheme.onSurfaceVariantSummary,
+            )
         }
     }
 }
@@ -211,14 +233,18 @@ private fun CenterHint(text: String) {
     }
 }
 
-private fun statusLabel(state: ChatUiState): String = when {
+/** 顶栏副标题：只反映连接状态。 */
+private fun connectionLabel(state: ChatUiState): String = when (state.connection) {
+    WsState.Connected -> "已连接"
+    WsState.Connecting -> "连接中…"
+    WsState.Reconnecting -> "重连中…"
+    WsState.Offline -> "离线"
+    WsState.Idle -> ""
+}
+
+/** 输入栏下方的忙碌提示。 */
+private fun busyLabel(state: ChatUiState): String = when {
     state.busyMode != null && state.queueDepth > 0 -> "正在思考… 已排队 ${state.queueDepth} 条"
     state.busyMode != null -> "正在思考…"
-    else -> when (state.connection) {
-        WsState.Connected -> "已连接"
-        WsState.Connecting -> "连接中…"
-        WsState.Reconnecting -> "重连中…"
-        WsState.Offline -> "离线"
-        WsState.Idle -> ""
-    }
+    else -> ""
 }

app/src/main/kotlin/top/yeij/cyrene/ui/chat/ChatViewModel.kt

@@ -304,6 +304,13 @@ class ChatViewModel(
         if (msg.sessionId != sessionId) return
 
         val clearStreaming = msg.role == "assistant"
+        // 流式结束：把这一轮的思维链挂到落库消息上，保留 10 分钟后再自动消失
+        val streamedThinking = if (clearStreaming) {
+            _state.value.streaming?.thinking?.takeIf { it.isNotBlank() }
+        } else {
+            null
+        }
+        val persisted = if (streamedThinking != null) msg.copy(thinking = streamedThinking) else msg
         if (clearStreaming) streamParser = null
 
         _state.update { state ->
@@ -314,11 +321,24 @@ class ChatViewModel(
                 state.pending
             }
             state.copy(
-                messages = mergeMessages(state.messages, listOf(msg)),
+                messages = mergeMessages(state.messages, listOf(persisted)),
                 pending = pending,
                 streaming = if (clearStreaming) null else state.streaming,
             )
         }
+
+        if (streamedThinking != null) {
+            viewModelScope.launch {
+                kotlinx.coroutines.delay(THINKING_LINGER_MILLIS)
+                _state.update { state ->
+                    state.copy(
+                        messages = state.messages.map {
+                            if (it.id == persisted.id) it.copy(thinking = null) else it
+                        },
+                    )
+                }
+            }
+        }
     }
 
     /** 上拉加载更早的一页。 */
@@ -358,3 +378,6 @@ class ChatViewModel(
 
 private fun Throwable.userMessage(): String =
     (this as? CyreneException)?.error?.userMessage ?: "加载失败，请稍后重试"
+
+/** 思维链在流式结束后继续保留的时长。 */
+private const val THINKING_LINGER_MILLIS = 10 * 60 * 1000L

app/src/main/kotlin/top/yeij/cyrene/ui/chat/StreamingBlocks.kt

@@ -33,7 +33,11 @@ fun ThinkingCard(
     modifier: Modifier = Modifier,
 ) {
     if (text.isBlank() && !active) return
-    var expanded by remember { mutableStateOf(true) }
+    // 流式期间展开（方便观察），流式结束自动折叠；历史思维链默认折叠。
+    var expanded by remember { mutableStateOf(active) }
+    LaunchedEffect(active) {
+        if (!active) expanded = false
+    }
 
     FoldCard(modifier = modifier, onClick = { expanded = !expanded }) {
         FoldCardHeader(