DropdownSelect / DropdownCascader overwrite the caller's aria-label with "Select"

[kemuru]

Version: 3.9.0 (also 3.8.0)

Both components spread the incoming props onto react-aria's Select and then set
aria-label={label ?? "Select"} after the spread:

• src/lib/dropdown/select/index.tsx (lines 48-53)
• src/lib/dropdown/cascader/index.tsx (lines 37-42)

So a consumer-supplied aria-label is always replaced by the literal "Select". Only
aria-labelledby survives, because it is forwarded by the spread.

Impact

Every dropdown rendered without a visible label is announced to screen readers as "Select",
regardless of what the app passes. Consumers end up writing wrappers to work around it, e.g.
web/src/components/LabeledDropdown.tsx in kleros/kleros-v2#2281, which renders a
visually-hidden span and points aria-labelledby at it.

Proposed fix

Only fall back to "Select" when nothing else labels the field, and let the spread win:

<AriaSelect
  className={cn("flex flex-col gap-1", className)}
  aria-label={label || props["aria-label"] || props["aria-labelledby"] ? undefined : "Select"}
  {...props}
  onSelectionChange={handleSelection}
>

Same change in the cascader. Alternatively, simply move the aria-label line above the
{...props} spread so consumer props take precedence.

Once released, the kleros-v2 wrapper can be deleted and callers pass aria-label directly.