feat(voice): 下行打字机文本流 + 首块快出，即时反馈

- protocol.go: 新增 ServerReply("reply") 消息——Agent 回答增量文本
- voice_tts.go: token 一到即转发客户端(打字机),同时攒句喂 TTS(音频随后)
- sentence_buffer.go: 本轮首句用低阈值(5 rune)抢首字延迟,之后回常规 12
- 桌面端 voice.ts onReply + VoiceDock 对话气泡(我说的 + JARVIS 打字机回答,思考态光标)

管线已最优:文字在 LLM 首 token 即刻上屏、音频紧随。剩余时延=大模型 TTFT(deepseek-v4-pro
4-7s 且波动大,疑似推理模型),这是模型的账、非管线——真要"马上响应"需换快模型。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-desktop/frontend/src/lib/voice.ts

@@ -14,6 +14,7 @@ export interface VoiceCallbacks {
   onState?: (s: VoiceState) => void;
   onTranscript?: (text: string, final: boolean) => void;
   onTask?: (taskId: string) => void;
+  onReply?: (deltaText: string) => void; // Agent 回答增量文本（打字机，逐 token）
   onError?: (msg: string) => void;
 }
 
@@ -115,6 +116,9 @@ export class VoiceClient {
         case "task":
           if (m.task_id) this.cb.onTask?.(m.task_id);
           break;
+        case "reply":
+          if (m.text) this.cb.onReply?.(m.text); // 打字机：回答增量文本
+          break;
         case "speaking":
           this.setState("speaking");
           break;

sundynix-desktop/frontend/src/shell/VoiceDock.tsx

@@ -24,8 +24,9 @@ export function VoiceDock({ onTask }: Props) {
   const toast = useToast();
   const clientRef = useRef<VoiceClient | null>(null);
   const [state, setState] = useState<VoiceState>("idle");
-  const [transcript, setTranscript] = useState("");
-  const [open, setOpen] = useState(false); // 是否展开转写气泡
+  const [transcript, setTranscript] = useState(""); // 我说的（ASR 转写）
+  const [reply, setReply] = useState(""); // JARVIS 回答（打字机，逐 token 累加）
+  const [open, setOpen] = useState(false); // 是否展开对话气泡
 
   // 懒建客户端（首次点按时，带上用户手势→AudioContext 才能启动）。
   const ensureClient = useCallback((): VoiceClient => {
@@ -38,7 +39,11 @@ export function VoiceDock({ onTask }: Props) {
         },
         onTask: (taskId) => {
           onTask(taskId);
-          setOpen(false);
+          setOpen(true); // 留着气泡显示打字机回答
+        },
+        onReply: (delta) => {
+          setReply((r) => r + delta); // 打字机：增量拼接，LLM 首 token 即刻可见
+          setOpen(true);
         },
         onError: (msg) => toast.push("error", msg),
       });
@@ -55,6 +60,7 @@ export function VoiceDock({ onTask }: Props) {
         c.stopListening();
       } else {
         setTranscript("");
+        setReply(""); // 新一轮：清上一轮的回答
         setOpen(true);
         await c.startListening(); // speaking 中会先打断再开新一轮
       }
@@ -68,11 +74,25 @@ export function VoiceDock({ onTask }: Props) {
 
   return (
     <div className="pointer-events-none fixed bottom-6 right-6 z-40 flex flex-col items-end gap-2">
-      {/* 转写气泡 */}
-      {open && transcript && (
-        <div className="pointer-events-auto max-w-xs rounded-2xl border border-line bg-ink-850/95 px-4 py-2.5 text-sm text-slate-200 shadow-xl backdrop-blur">
+      {/* 对话气泡：我说的（转写）+ JARVIS 回答（打字机） */}
+      {open && (transcript || reply) && (
+        <div className="pointer-events-auto max-w-xs rounded-2xl border border-line bg-ink-850/95 px-4 py-3 text-sm shadow-xl backdrop-blur">
           <div className="flex items-start gap-2">
-            <span className="flex-1 leading-relaxed">{transcript}</span>
+            <div className="flex-1 space-y-1.5">
+              {transcript && (
+                <p className="leading-relaxed text-slate-400">
+                  <span className="mr-1 text-[11px] text-slate-500">我</span>
+                  {transcript}
+                </p>
+              )}
+              {reply && (
+                <p className="leading-relaxed text-slate-100">
+                  <span className="mr-1 text-[11px] text-brand-300">JARVIS</span>
+                  {reply}
+                  {state === "thinking" && <span className="ml-0.5 inline-block h-3.5 w-[2px] translate-y-[2px] animate-pulse bg-brand-300 align-middle" />}
+                </p>
+              )}
+            </div>
             <button className="mt-0.5 text-slate-500 hover:text-slate-300" onClick={() => setOpen(false)} aria-label="收起">
               <X className="h-3.5 w-3.5" />
             </button>