NAWS mid-session updates now propagate to the window stack: Application
re-runs each open window's relayout on resize. Window#relayout re-centers
(clamped to the screen edge) by shifting all descendants; MasterDetail
recomputes its full geometry and re-renders the detail at the new width.
ButtonBar placement is extracted into ButtonBar.place for reuse.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
