`config` query string sometimes removed after clicking "Build" button

Description:

When clicking the Build button, the config query string in the URL is sometimes removed unexpectedly. This doesn’t happen consistently—I'd estimate it occurs around 50% of the time.

The issue seems to occur more reliably when:

• The URL includes both config and bundle query strings.
• The Build button is clicked while the initial auto-build (triggered on page load) is still in progress.

I've attached a video to demonstrate the behavior. Please watch the Chrome address bar closely after clicking the Build button.

Here’s an example link to reproduce the issue: https://bundlejs.com/?q=%40szhsin%2Freact-accordion&treeshake=%5B*%5D&config=%7B%22esbuild%22%3A%7B%22external%22%3A%5B%22react%22%2C%22react-dom%22%5D%7D%7D&bundle

Impact:

Because the config query string is removed, the bundle size calculation is incorrect. For example:

• With the config query string, the bundle size is 2.92 kB (gzip)
• Without the config query string, the bundle size jumps to 6.11 kB (gzip)

Expected Behavior:

The config query string should remain in the URL after clicking the Build button.

https://github.com/user-attachments/assets/6954a27d-fe53-4f32-80e9-feae0f13f882

Start by reproducing the issue with the example URL and inspect the Build button flow while the initial auto-build is still running. Trace how the config and bundle query strings are handled after the click. Done means config remains in the URL and the bundle size still reflects that configuration.