fix: remove character entity references in rebuild:audio script command

[mogul]

Description

This PR fixes a syntax error in the rebuild:audio npm script inside package.json.

Impact

I noticed that the pre-built release AppImage doesn't contain the correct audio build for Linux (CachyOS). It's likely that when this release was produced, the audio build wasn't recompiled from Windows due to the package.json command being borked.

I've been debugging since I downloaded the Linux release, I go to Plugins > Audio > '+ NAM' > Select NAM file, but nothing happens. It does not get updated in the UI. Running npm run rebuild:audio fixes this, but only after this patch.

Root Cause

The script command had an HTML-encoded && instead of &&. This caused the command to fail immediately when attempting to run a clean build of the audio engine:

# Before (Fails)
"rebuild:audio": "rm -rf build && bash scripts/build-audio.sh Release"

# After (Succeeds)
"rebuild:audio": "rm -rf build && bash scripts/build-audio.sh Release"

Reconstructed from `slopsmith/slopsmith-desktop#290` — original PR by @mikebyte00. Commits replayed with original authorship onto the current `main`.