The preview effect still depended on componentMetadata BY IDENTITY. For
components that is stable (the registry hands back the same object), but for
BOARDS the canvas builds the metadata inline per render, so every parent
re-render - which a pointer moving over the canvas causes - tore the preview
element down and rebuilt it. The dialog visibly resized and snapped back.
It now keys on a digest of the metadata (id, tagName, defaults) and reads the
object through a ref, joining propsKey and pinsKey which were fixed the same
way earlier. Nothing rebuilds unless something real changed.
a1307f117d