`PlotItem.addItem()` records overlays outside the Qt scene. Direct
scene removal leaves stale plot refs and range bookkeeping behind.
Track each annotation's owning plot and remove it through the same
API used for insertion. Exclude pixel-sized arrows from data
bounds.
Deats,
- centralize replacement, hiding and owner teardown;
- retain scene removal as a defensive fallback;
- cover real Qt registries and duplicate-FQME chart identity.
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
Gud Boi
78982d8280