Replace free-form fractional HUD widget positioning with a 4x8 int grid
(col/row/colSpan/rowSpan), reject drag/resize moves that would overlap
another visible widget, and re-place a re-enabled metric into the next
free grid slot instead of stacking it on an occupier. Drag/resize now
track a local pixel offset during the gesture and only snap/commit once
at gesture end. HUD widget text is wrapped in FittedBox(scaleDown) so it
never overflows and stays centered at any grid size.
