Fix gizmo being closed after releasing mouse outside the gizmo floating window (#15095)

* Fix gizmo being closed after releasing mouse outside the gizmo floating window

The left up event of a drag started on the gizmo floating window (e.g.
selecting text in an input field) and released over the bed was treated
as a click on the plate, which deselected the objects and closed the
active gizmo. Add the ignore_left_up guard to the plate select branch,
matching the deselect branch above.

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix Emboss gizmo being closed after releasing mouse outside its floating window

The Emboss gizmo has its own close-on-click-away handler
(on_mouse_change_selection) that was not protected against left up events
originating from ImGui windows, so the gizmo was still closed when a drag
started on its floating window (e.g. selecting text in the input field)
ended over the 3D scene. Expose the canvas's ignore_left_up state to
gizmos and skip the close check for such releases.

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/slic3r/GUI/GLCanvas3D.hpp

@@ -1119,6 +1119,10 @@ public:
 
     void set_mouse_as_dragging() { m_mouse.dragging = true; }
     bool is_mouse_dragging() const { return m_mouse.dragging; }
+    // True when the current left up event comes from an ImGui window and was not processed by it
+    // (e.g. a drag that started on a gizmo floating window and was released over the 3D scene).
+    // Such a release is the end of an ImGui interaction, not a click on the scene.
+    bool is_mouse_left_up_ignored() const { return m_mouse.ignore_left_up; }
 
     double get_size_proportional_to_max_bed_size(double factor) const;