test: include pipelines audio in root vitest projects (#2419)

## Summary

- add `packages/pipelines-audio` to the root Vitest project list

## Why

`packages/pipelines-audio` has a package-local Vitest config and seven
test files, but the root `vitest.config.ts` did not include it. As a
result, the normal root test entry did not execute this package's tests.
The other packages mentioned in the original backlog candidate are
already included or no longer exist on current `main`, so this PR is
limited to the remaining gap.

## Verification

- `git diff --check`
- package manifest resolution via `pnpm --filter
@proj-airi/pipelines-audio list --depth=-1`
- static comparison with `packages/pipelines-audio/vitest.config.ts` and
its current test files

The full root Vitest run was not started because dependencies are not
installed in this filtered clone.

Co-authored-by: ming <silverchris@foxmail.com>
Co-authored-by: Columbina <140679517+0xSelenicDove@users.noreply.github.com>

vitest.config.ts

@@ -13,6 +13,7 @@ export default defineConfig({
       'packages/ccc',
       'packages/core-agent',
       'packages/i18n',
+      'packages/pipelines-audio',
       'packages/input-gamepad',
       'packages/input-gamepad-vueuse',
       'packages/input-playstation-dualsense-5',