Design for rewriting the installer to fetch prebuilt binaries from Gitea
Releases on git.kuns.dev instead of building from source. Covers the
Actions workflow, release artifact layout, install.json marker file,
Install/Update/Manage mode detection, and the new DownloadAndExtractStep.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
