Port pgt TUI spike to pyratatui Terminal loop.
Summary of changes:

* Replace the unicurses app shell with pyratatui Terminal/Frame drawing and KeyEvent input, starting with Help and NoRepo pages plus a shared keys helper.
* port pgt TUI theme to pyratatui Style
* Map Git color specs to Style/Color instead of curses color pairs so widgets can consume the theme directly.
* port pgt home chrome to Layout and Tabs
* Rebuild the home header with constraint layouts, the Tabs widget, and KeyEvent-based navigation modes.
* port status, log, and tasks lists to List widget
* Drive home tab content with pyratatui List/ListState and TextState for commit message input.
* port overlay pages to List and TextState
* Rewrite projects, branch picker, and task editor around List and TextPrompt/TextState instead of hand-drawn rows.
* remove unicurses from pgt TUI
* Delete the unicurses adapter and draw helpers, drop the uni-curses dependency, and update remaining tests for pyratatui.
* modify how git refreshes are triggered with ratatui's render model
* fix off-by-one error after converting to ratatui Lists
* fix input bug handling 'q'