fix(board): make container headers fully clickable (#7006)

apps/docs/docs/management/boards/index.mdx

@@ -50,7 +50,8 @@ was introduced; widen the affected Container before moving widgets into its righ
 ### Containers and rails
 
 A **Container** groups apps, widgets, and nested Containers. It can have a label, collapse control, app-opening action,
-border color, and CSS classes.
+border color, and CSS classes. Click anywhere on a collapsible Container’s header to collapse or expand it.
+The header also supports Enter and Space; its app-opening action and edit controls work independently.
 
 Items can occupy the outermost rows and columns of a Container. The drop preview shows the position where the item
 will remain when released.