replace the editor menubar dropdown flow with a reusable context menu
component
merge sprite/entity placement into a single object tool
persist entities, and add undo
support for created sprites and entities

full-width toolbar/menubar layer
move save into file menu and add edit menu actions for undo/redo
menubar dropdown interaction modal
update header/view-type labels and menu layout behavior
creation-history tracking for walls and polygons
undo (ctrl+z) and redo (ctrl+r) in 2d editor
improve list/button visual states

add responsive editor relayout for window resize
rework header with back/save, view mode buttons, and 2d view type selector
add clipped, scrollable assets and contextual tool panels
simplify tool button wiring and repeated layout logic
simplify 2d top-down editor internals and shared grid update hooks