scss is not compiled correctly in vue sfc

[LateDreamXD]

Reproduction link or steps

// package.json
{
  // ...,
  "dependencies": {
    "vue": "^3.5.30"
  },
  "devDependencies": {
    // ...,
    "@tsdown/css": "^0.21.4",
    "sass-embedded": "^1.98.0",
    "tsdown": "^0.21.4",
    "typescript": "^5.9.3",
    "unplugin-vue": "^7.1.1",
    "vue-tsc": "^3.2.6"
  }
}

// tsdown.config.ts
// ...;

export default defineConfig({
	deps: {
		alwaysBundle: ['vue']
	},
	entry: { content: 'src/content/index.ts' },
	plugins: [vue()],
	css: {
		fileName: 'content.css',
		target: 'chrome140'
	},
	platform: 'browser',
	minify: true,
	format: 'iife',
	tsconfig: 'tsconfig.app.json'
});

// src/content/index.ts
import { createApp } from 'vue';
import App from './App.vue';

createApp(App).mount('#app');

<!-- src/content/App.vue -->
<template><!-- ... --></template>

<style lang="scss" scoped>
@mixin shared {
  // shared
}
.el1 {
  @include shared;
  // el1
}
.el2 {
  @include shared;
  // el2
}
</style>

What is expected?

/** dist/content.css */
.el1 {
  /** shared */
  /** el1 */
}

.el2 {
  /** shared */
  /** el2 */
}

What is actually happening?

/** dist/content.css */
@mixin shared {
  /** shared */
}

@include shared;
@include shared;

Any additional comments?

No response

[wChenonly]

can you provide a minimal reproducible example?

[LateDreamXD]

sure, here is: LateDreamXD/demo

[wChenonly]

sure, here is: LateDreamXD/demo

get，I am trying to fix a bug.