CI: developers can get unminified VSIX artifact for each commit

## Problem

1. Sometimes we need the unminified form of a VSIX, for debugging in browser context (cloud9, etc.).
2. our GHA tasks don't produce any artifacts. This makes it more complicated for automation scripts to discover the artifacts.
- the codebuild artifacts expire after 1-2 weeks
- the codebuild artifact URLs are not easily discoverable by automation

## Solution

1. Enhance the GHA workflow to product VSIX artifacts:
- minified
- unminified

Start by locating the GitHub Actions workflow that builds the VSIX and inspect how the current CodeBuild artifacts are produced. Done means each commit's workflow exposes both minified and unminified VSIX artifacts through discoverable GitHub Actions artifacts, with retention suitable for automation.

Written by the indexing model from the issue text.