🚧 Highlighting

There is no general-purpose "highlight this shape" API (a setter that paints an arbitrary accent ring around any element on demand). What the editor does have is a set of contextual hover highlights, drawn by the overlay during specific interactions:

• Container drop target — while dragging a shape over a container, the hovered container's drop-zone is drawn as a dashed accent rectangle (Editor.containerHover).
• Link attachment — in draw-edge mode the element under the cursor is highlighted, and its anchor dots grow as the pointer nears them, so you can see where a connector will attach (Editor.hoveredLinkTarget).
• Annotation focus — the focused annotation thread's pin gets an accent ring (Editor.setSelectedAnnotation).

These are view-only overlay states, recomputed each frame from the current gesture; they are never recorded in history or persisted. The persistent selection halo around selected shapes and links is separate — see Selection.

For accessibility, the editor also emits short live-region strings (for example "Selected Rectangle") via Editor.onAnnounce, which a host pipes into an aria-live region.

Planned — not yet available: a programmatic highlight API to mark arbitrary shapes (for search results, validation errors, or guided tours) with a custom colour, independent of selection and hover. Today, build this with the renderer's overlay extension points and your own state.