[italomlp]

Dragging a floating window can leave its focus hint at the old position, and stack tabs can appear above a floating window covering their stack. A window converted from stacked to floating can also remain the tab bar's active owner until the next rebuild.

Hide the hint during move/resize, guard immediate and deferred hint callbacks while grabbed or settling, and clear grab state even for floating windows without a tiling grab operation. Post-grab settling accepts an already-committed frame. Defer and coalesce stack-tab restacking until BEFORE_REDRAW, cancel callbacks on destruction, and avoid unnecessary tab reparenting. When the active tab is removed, immediately transfer ownership and geometry signals to a remaining tab, clear stale previous ownership, and schedule restacking.

Validation:

• 15 regression tests pass, exercising production methods with GNOME boundary doubles. Coverage includes floating/tiled grab cleanup, stale callbacks, settling, layering, callback disposal, active-tab removal at each position, and preservation of an inactive tab's owner.
• ESLint, TypeScript checks, and clean make pack builds pass. Both packages contain the required files, have no forbidden extension-process Gdk imports, and meet the 10 MB size limit.
• The reporter tested the combined local build on Ubuntu 26.04.1 / GNOME 50.1 and confirmed the reported rendering issues, including stacked-to-floating conversion, are resolved.

The desktop verification covers the reporter's setup; it does not establish behavior across every compositor/display configuration. This change is independent of #112.