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.
Introduce SmoothTabWidget and a FadingStackedWidget to provide cross-fade transitions between tabs. Added ytsage/gui/ytsage_smooth_tab_widget.py which implements a QTabBar + FadingStackedWidget (default 300ms fade) and overlay-based fade logic. Updated ytsage/gui/ytsage_gui_dialogs/ytsage_dialogs_custom.py to use SmoothTabWidget instead of QTabWidget and adjusted the stylesheet selector to target the new content frame (#tabContent) so existing styles continue to apply.
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.