feat(chat): 回车发送 + 长按气泡复制

输入框 imeAction=Send（回车即发送）；长按气泡体复制原文到剪贴板并 Toast 提示。

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

@@ -16,6 +16,8 @@ import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
 import androidx.compose.foundation.lazy.rememberLazyListState
+import androidx.compose.foundation.text.KeyboardActions
+import androidx.compose.foundation.text.KeyboardOptions
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
@@ -26,6 +28,7 @@ import androidx.compose.runtime.setValue
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.input.ImeAction
 import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.lifecycle.viewmodel.initializer
@@ -195,6 +198,8 @@ private fun InputBar(
                 label = "和昔涟说点什么…",
                 useLabelAsPlaceholder = true,
                 maxLines = 5,
+                keyboardOptions = KeyboardOptions(imeAction = ImeAction.Send),
+                keyboardActions = KeyboardActions(onSend = { onSend() }),
                 modifier = Modifier.weight(1f),
             )
             Spacer(Modifier.width(8.dp))

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

@@ -0,0 +1,32 @@
+package top.yeij.cyrene.ui.chat
+
+import android.content.ClipData
+import android.content.ClipboardManager
+import android.content.Context
+import android.widget.Toast
+import androidx.compose.foundation.gestures.detectTapGestures
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.platform.LocalContext
+
+/**
+ * 长按复制文本到系统剪贴板，并给一条 Toast 反馈。
+ * 用框架的 ClipboardManager 而不是 Compose 的 LocalClipboardManager（后者在新版本已弃用）。
+ */
+@Composable
+fun Modifier.copyOnLongPress(text: String): Modifier {
+    if (text.isBlank()) return this
+    val context = LocalContext.current
+    return this.pointerInput(text) {
+        detectTapGestures(
+            onLongPress = { copyToClipboard(context, text) },
+        )
+    }
+}
+
+private fun copyToClipboard(context: Context, text: String) {
+    val clipboard = context.getSystemService(Context.CLIPBOARD_SERVICE) as ClipboardManager
+    clipboard.setPrimaryClip(ClipData.newPlainText("Cyrene", text))
+    Toast.makeText(context, "已复制", Toast.LENGTH_SHORT).show()
+}

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

@@ -143,6 +143,7 @@ private fun BubbleBody(text: String, isUser: Boolean) {
     Box(
         modifier = Modifier
             .widthIn(max = 300.dp)
+            .copyOnLongPress(text)
             .background(
                 color = if (isUser) {
                     MiuixTheme.colorScheme.primary