`vp build` hangs indefinitely when `sass-embedded` is used — CLI does not call `process.exit()` after successful build

[ilkobg]

Describe the bug

vp build completes the build successfully but the process never exits when sass-embedded is installed as the Sass compiler. The Dart VM child process spawned by sass-embedded keeps the Node event loop alive indefinitely.

Root cause (two layers):

1. Upstream Vite bug ([Bug]: sass-embedded ChildProcess outlives server.close() - cssPlugin teardown drops worker.stop() promise vitejs/vite#22274): Vite's scssProcessor.close() is synchronous but calls async stop() which awaits compiler.dispose(). The promise is dropped, so the sass-embedded Dart subprocess is never shut down. Since vite-plus-core bundles Vite's CSS plugin code, this bug is present in Vite+ as well.

2. Vite+ CLI behavior: vp build does not call process.exit(0) after a successful build. It relies on the Node event loop draining naturally. When any plugin or preprocessor leaves a handle open (like sass-embedded's persistent ChildProcess), the process hangs forever.

This is the same class of issue as #1396 — the CLI is not resilient against lingering event loop handles from third-party tools.

Reproduction

1. In any Vite+ project that uses SCSS:

vp install sass-embedded
vp uninstall sass

2. Run vp build
3. The build output completes successfully (~19s in our case), but the process hangs at 100% and never exits
4. lsof -p <pid> shows an orphaned Dart child process keeping the event loop alive

Expected behavior

vp build should exit with code 0 after the build completes, regardless of whether preprocessor plugins have properly cleaned up their handles.

Suggested fix

Short-term (Vite+ side): Add an explicit process.exit(0) in the vp build CLI path after successful build completion. This is a defense-in-depth measure that makes the CLI resilient to handle leaks from any plugin or preprocessor — not just sass-embedded.

Long-term (upstream): Once vitejs/vite#22274 is fixed and the updated Vite source is re-bundled into vite-plus-core, the Dart subprocess will be properly disposed and the event loop will drain naturally. The explicit process.exit(0) would still be good practice as a safety net.

Workaround

Use sass (Dart Sass compiled to JavaScript) instead of sass-embedded. Same API, same output, but runs in-process with no child process — so the event loop drains naturally after build.

System Info

vp: v0.1.16
sass-embedded: ^1.99.0
Node: 22.x
OS: macOS arm64

Validations

• Read the Contributing Guidelines.
• Check that there isn't already an issue for the same bug.
• Confirm this is a Vite+ issue and not an upstream issue — partially upstream ([Bug]: sass-embedded ChildProcess outlives server.close() - cssPlugin teardown drops worker.stop() promise vitejs/vite#22274), but vp build not calling process.exit() is specific to Vite+.
• The provided reproduction is a minimal reproducible example.