feat: M5 外观特效选择+持久化（appearance:load/save IPC+config.json，鼠效 6 选格接 EffectEngine，重开恢复并接线）

apps/desktop/src/main/ipc/handlers.ts

@@ -50,6 +50,9 @@ export function registerIpc(vault: VaultService) {
     const gd = await buildGraphData(fs2.getRoot(), tree); return gd;
   });
 
+  ipcMain.handle(IPC.appearanceLoad, async () => vault.getAppearance());
+  ipcMain.handle(IPC.appearanceSave, async (_e, p: { themeId: string; params: Record<string, unknown>; effect: string }) => { await vault.saveAppearance(p); });
+
   ipcMain.handle(IPC.copyMd, async (_e, p: { path: string }) => {
     const fs2 = vault.fileService; if (!fs2) return '';
     const { body } = await fs2.readDoc(p.path);