The canvas had no tabindex, so clicking on it didn't move focus away
from previously focused input elements. When document.activeElement
was still an input/textarea (e.g. from a panel interaction), the
keyboard shortcut guard treated Backspace as blocked by an active
input — making it impossible to delete selected nodes via the canvas.
- Add tabindex="-1" + outline-none to the canvas element
- Explicitly focus canvas on mousedown (except during text editing)
Fixes#220
44484050e2