Build the context-menu model for a right-click target.
item === null → empty-canvas menu: add sticky / text / markdown panel / widget
at the click point (the board routes these through its existing placement paths),
plus "New page" (the same path as the strip's "+" button);
highlight → Delete only (highlights are transient "pointing" chrome);
any other item → Edit (same path as dblclick; editable kinds only), Restyle…
(text/sticky), Duplicate (not connectors/highlights), Bring to front / Send to
back, and Delete.
Build the context-menu model for a right-click target.
item === null→ empty-canvas menu: add sticky / text / markdown panel / widget at the click point (the board routes these through its existing placement paths), plus "New page" (the same path as the strip's "+" button);