After a Wayland surface re-creation (tray hide/show, miniplayer cycle),
reset_canvas swapped in a fresh canvas but kept graphics_cache and
texture_cache entries whose textures belong to the OLD canvas's image
store. A cache-rendering-hint layer (Sidebar/HeaderBar/NowPlayingBar
since e3257631) then blits a dangling image id: the subtree goes
invisible while layout and hit-testing keep working — exactly the
reported 'sidebar content does not render' after a
miniplayer->theme->sidebar journey. set_window_adapter and
clear_graphics_context already clear both caches; reset_canvas now does
too (layers re-render, images re-upload once per re-creation).
km