fix: 修复播放并发控制死代码、shallowRef响应式、歌词IPC高频调用 (H-005/H-006/H-009)

- H-005: 删除 playerCore.ts 中无效的 playInProgress 局部变量
- H-006: fetchSongs 修改 shallowRef 元素后添加 triggerRef 触发更新
- H-009: sendLyricToWin 从每秒20次全量发送改为每秒5次轻量更新

src/renderer/store/modules/playerCore.ts

@@ -335,17 +335,8 @@ export const usePlayerCoreStore = defineStore(
           console.warn('预加载触发失败（可能是依赖未加载或循环依赖），已忽略:', e);
         }
 
-        let playInProgress = false;
-
         try {
-          if (playInProgress) {
-            console.warn('播放操作正在进行中，避免重复调用');
-            return true;
-          }
-
-          playInProgress = true;
           const result = await playAudio(requestId);
-          playInProgress = false;
 
           if (result) {
             playbackRequestManager.completeRequest(requestId);
@@ -356,7 +347,6 @@ export const usePlayerCoreStore = defineStore(
           }
         } catch (error) {
           console.error('自动播放音频失败:', error);
-          playInProgress = false;
           playbackRequestManager.failRequest(requestId);
           return false;
         }

src/renderer/store/modules/playlist.ts

@@ -1,7 +1,7 @@
 import { useThrottleFn } from '@vueuse/core';
 import { createDiscreteApi } from 'naive-ui';
 import { defineStore, storeToRefs } from 'pinia';
-import { computed, ref, shallowRef } from 'vue';
+import { computed, ref, shallowRef, triggerRef } from 'vue';
 
 import i18n from '@/../i18n/renderer';
 import { useSongDetail } from '@/hooks/usePlayerHooks';
@@ -83,6 +83,8 @@ export const usePlaylistStore = defineStore(
             playList.value[startIndex + index] = song;
           }
         });
+        // 触发 shallowRef 响应式更新（直接修改元素不会自动触发）
+        triggerRef(playList);
 
         // 预加载下一首歌曲的音频和封面
         if (nextSong) {