Introduce an opt-in beta updates feature: add a styled "Receive Beta Updates" checkbox in the Updater UI with i18n strings, load/save logic in the custom options dialog, and a default config key (check_beta_updates=false).
Add _fetch_github_beta_version to the update thread to query GitHub releases (selecting the highest tag) and emit update_available for newer beta builds. When beta checking is enabled, the thread will perform the GitHub beta check and return early to avoid conflicting with the PyPI check. This enables users to opt into preview releases safely.
Add streaming progress support to Deno upgrades and hook it into the GUI. upgrade_deno() now accepts an optional progress_callback and uses subprocess.Popen to read stdout line-by-line (line-buffered, utf-8, errors replaced), collecting output and invoking the callback as lines arrive. Added DenoUpdateThread (QThread) with finished/progress/error signals and replaced the previous background thread usage in the updater UI with this QThread. GUI slots strip ANSI escapes, truncate long messages, and update status text; buttons are re-enabled on finish/error. Improved logging and error handling for upgrade failures.
Moved all files from src/gui/ to ytsage/gui/ and updated import statements to use relative imports within the new package structure. This improves modularity and prepares the codebase for distribution as a proper Python package.