Fix code-size CI: use deploy script that exists on both branches

The compressed-size-action checks out master and runs the build script.
Master doesn't have a root "build" script, so revert to using "deploy"
which exists on both branches.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/code-size.yml

@@ -22,5 +22,5 @@ jobs:
       - uses: preactjs/compressed-size-action@v2
         with:
           repo-token: "${{ secrets.GITHUB_TOKEN }}"
-          build-script: "build"
+          build-script: "deploy"
           pattern: "./packages/webamp/built/*bundle.min.js"