The CSS rule `.scad-panel { display: flex }` was overriding the HTML
`hidden` attribute (CSS specificity beats the user-agent rule on the
attribute). Effect: the Close button set hidden=true but the panel
stayed visible, and the panel was visible on first load too.
- Explicit `.scad-panel[hidden] { display: none }` rule restores the
intended behaviour: Close hides, initial load is hidden.
- Default height 45% -> 30%, with min-height 180px so the editor
isn't cramped even on small viewports.
wenil
73c9495a96