* feat(ds): elevate dropdown overlays and stabilize selection check gutter
Menus and popovers floated at the same elevation as inline cards
(shadow-border-xs), so dropdowns blended into the content beneath them.
Bump DS::Menu and DS::Popover panels to shadow-border-lg.
DS::MenuItem rendered its leading icon only when present, so a selection
check shifted the row's text out of alignment with the unselected rows.
Add a `selected:` param that reserves a fixed-width check gutter (check
when selected, empty otherwise) so row text stays aligned. Apply the same
reserved gutter to the bespoke category dropdown row, and add a
`selectable` menu preview.
* fix(ds): expose menu selection via menuitemradio + aria-checked
Selectable DS::MenuItem rows conveyed selection only visually. Render them
as role="menuitemradio" with aria-checked so assistive tech gets the
selection state of single-select lists, merging the menu ARIA contract with
any caller-supplied aria. Addresses CodeRabbit review feedback.
* fix(ds): include selectable roles in menu roving-focus query
DS::MenuItem selectable rows render as role=menuitemradio, but the menu
controller built its roving-focus list from [role=menuitem] only, leaving
single-select menus with no keyboard focus/arrow handling. Query the
menuitemradio/menuitemcheckbox roles too. Addresses Codex review feedback.
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