data-tauri-drag-region only fires when the exact element is the event target
and was never runtime-verified; replace it with the official Tauri custom-
titlebar recipe — primary-button mousedown starts an OS drag, detail===2
toggles maximize. Works across the whole region (brand text included, which
already passes pointer events through).
Pairs with cinny-desktop set_custom_chrome Mica fix (clear backdrop before
undecorating; window-state no longer restores the decorated flag).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>