feat(record): P4 暂停/继续 —— record pause/resume 子命令 + CaptureHandle.pause/resume

SPEC_RealtimeTranscript_UX_V1 §五：
- cli.py：新增  / （状态文件 pid
  定位 + SIGUSR1 通知前台进程）；前台进程注册 SIGUSR1 handler 切换
  handle.pause()/resume()；状态文件记录 paused 供 status 显示
- audio_capture.py：CaptureHandle.pause()/resume() —— 采集回调丢弃帧
  + 向 Cloud WS 发 pause/resume 控制消息（云端计费暂停）；is_paused 属性
- record status 显示 ⏸️/🎙️ 状态

mindcli/cli.py

@@ -56,6 +56,13 @@ def _save_state(state: dict) -> None:
         json.dump(state, f, ensure_ascii=False)
 
 
+def _patch_state(patch: dict) -> None:
+    """合并更新状态文件（record start 进程内调用）。"""
+    state = _load_state() or {}
+    state.update(patch)
+    _save_state(state)
+
+
 def _clear_state() -> None:
     try:
         _STATE_FILE.unlink()
@@ -140,6 +147,17 @@ async def _run_capture(capture_audio, ws_url, chat_id, meeting_id, source, on_te
     loop.add_signal_handler(signal.SIGINT, stop_event.set)
     loop.add_signal_handler(signal.SIGTERM, stop_event.set)
 
+    # P4：SIGUSR1 = 暂停/继续切换（由 `mind record pause/resume` 触发）
+    def _toggle_pause() -> None:
+        if handle.is_paused:
+            handle.resume()
+            _patch_state({"paused": False})
+        else:
+            handle.pause()
+            _patch_state({"paused": True})
+
+    loop.add_signal_handler(signal.SIGUSR1, _toggle_pause)
+
     try:
         await stop_event.wait()
     finally:
@@ -159,6 +177,36 @@ def record_stop():
     click.echo(f"⏹️ 已发送停止信号 pid={state['pid']}")
 
 
+@record.command(name="pause")
+def record_pause():
+    """暂停录音（向 record start 进程发 SIGUSR1）。"""
+    state = _load_state()
+    if not state or not _pid_alive(state.get("pid", -1)):
+        click.echo("⏹️ 未在录音")
+        return
+    if state.get("paused"):
+        click.echo("⏸️ 已处于暂停")
+        return
+    os.kill(state["pid"], signal.SIGUSR1)
+    _patch_state({"paused": True})
+    click.echo(f"⏸️ 已暂停 pid={state['pid']}")
+
+
+@record.command(name="resume")
+def record_resume():
+    """继续录音（向 record start 进程发 SIGUSR1）。"""
+    state = _load_state()
+    if not state or not _pid_alive(state.get("pid", -1)):
+        click.echo("⏹️ 未在录音")
+        return
+    if not state.get("paused"):
+        click.echo("🎙️ 未处于暂停")
+        return
+    os.kill(state["pid"], signal.SIGUSR1)
+    _patch_state({"paused": False})
+    click.echo(f"🎙️ 已继续 pid={state['pid']}")
+
+
 @record.command(name="status")
 def record_status():
     """查看录音状态。"""
@@ -167,7 +215,8 @@ def record_status():
         click.echo("⏹️ 未在录音")
         return
     duration = round(time.time() - state.get("startedAt", time.time()), 1)
-    click.echo(f"🎙️ 录音中 duration={duration}s chatId={state.get('chatId', '')} "
+    paused = "⏸️ 已暂停" if state.get("paused") else "🎙️ 录音中"
+    click.echo(f"{paused} duration={duration}s chatId={state.get('chatId', '')} "
                f"source={state.get('source')} meetingId={state.get('meetingId')}")