feat(opal): clickable SelectCards are keyboard-operable (#14997)

web/lib/opal/src/components/cards/select-card/README.md

@@ -22,6 +22,12 @@ The key differences:
 - SelectCard has no `foldable` prop — use `Interactive.Foldable` directly inside children.
 - SelectCard's children are fully composable — use `CardHeaderLayout`, `ContentAction`, `Content`, buttons, etc. inside.
 
+## Keyboard
+
+The root is a `<div>` so children can be buttons and links, which HTML forbids inside a `<button>`. A card with `onClick` joins the tab order and fires `onClick` on Enter or Space. While keyboard-focused it paints exactly like hover, so pointer and keyboard users see the same affordance. Keys pressed on a nested control never reach the card. A nested button that only repeats the card's action can leave the tab order with `tabIndex={-1}`.
+
+The card takes no ARIA role of its own. A role such as `button` would fold every nested button into the card's accessible name, which is wrong for cards that host their own actions. A card that is one action can pass `role` and `aria-label` itself; a caller's `tabIndex` also wins over the default.
+
 ## Architecture
 
 ```

web/lib/opal/src/components/cards/select-card/components.tsx

@@ -55,6 +55,12 @@ type SelectCardProps = Omit<InteractiveStatefulProps, "variant"> & {
  * Stateful system owns background and foreground colors; the card owns
  * padding, rounding, border, and overflow.
  *
+ * The root stays a `<div>` so children can be buttons and links, which HTML
+ * forbids inside a `<button>`. A card with `onClick` still joins the tab
+ * order, opens on Enter or Space, and paints like hover while
+ * keyboard-focused. It takes no ARIA role of its own: a role would fold any
+ * nested button into the card's accessible name.
+ *
  * Children are fully composable — use `ContentAction`, `Content`, buttons,
  * `Interactive.Foldable`, etc. inside.
  *
@@ -76,13 +82,39 @@ function SelectCard({
   border = "solid",
   ref,
   children,
+  onClick,
+  onKeyDown,
+  disabled,
   ...statefulProps
 }: SelectCardProps) {
   const paddingStyle = { padding: spacingToRem(paddingProp) };
   const radius = roundingToRem(roundingProp);
 
+  // A caller with its own tab index (e.g. a roving radio group) keeps it.
+  const isControl = !!onClick && !disabled;
+  const controlProps = isControl
+    ? {
+        tabIndex: statefulProps.tabIndex ?? 0,
+        onKeyDown: (event: React.KeyboardEvent<HTMLElement>) => {
+          onKeyDown?.(event);
+          if (event.defaultPrevented) return;
+          // Keys pressed on a nested control belong to that control.
+          if (event.target !== event.currentTarget) return;
+          if (event.key !== "Enter" && event.key !== " ") return;
+          event.preventDefault();
+          event.currentTarget.click();
+        },
+      }
+    : { onKeyDown };
+
   return (
-    <Interactive.Stateful {...statefulProps} variant="select-card">
+    <Interactive.Stateful
+      {...statefulProps}
+      {...controlProps}
+      onClick={onClick}
+      disabled={disabled}
+      variant="select-card"
+    >
       <div
         ref={ref}
         className="opal-select-card"

web/lib/opal/src/components/cards/select-card/styles.css

@@ -6,6 +6,12 @@
   @apply w-full overflow-clip;
 }
 
+/* Keyboard focus paints like hover (see Interactive.Stateful), so the
+   default focus ring would double up. */
+.opal-select-card:focus-visible {
+  outline: none;
+}
+
 /* Border color */
 .opal-select-card[data-interactive-state="selected"] {
   border-color: var(--interactive-foreground);

web/lib/opal/src/core/interactive/stateful/styles.css

@@ -150,6 +150,9 @@
 .interactive[data-interactive-variant="select-card"][data-interactive-state="empty"]:hover:not(
   [data-disabled]
 ),
+.interactive[data-interactive-variant="select-card"][data-interactive-state="empty"]:focus-visible:not(
+  [data-disabled]
+),
 .interactive[data-interactive-variant="select-card"][data-interactive-state="empty"][data-interaction="hover"]:not(
   [data-disabled]
 ) {
@@ -183,6 +186,9 @@
 .interactive[data-interactive-variant="select-card"][data-interactive-state="filled"]:hover:not(
   [data-disabled]
 ),
+.interactive[data-interactive-variant="select-card"][data-interactive-state="filled"]:focus-visible:not(
+  [data-disabled]
+),
 .interactive[data-interactive-variant="select-card"][data-interactive-state="filled"][data-interaction="hover"]:not(
   [data-disabled]
 ) {
@@ -216,6 +222,9 @@
 .interactive[data-interactive-variant="select-card"][data-interactive-state="selected"]:hover:not(
   [data-disabled]
 ),
+.interactive[data-interactive-variant="select-card"][data-interactive-state="selected"]:focus-visible:not(
+  [data-disabled]
+),
 .interactive[data-interactive-variant="select-card"][data-interactive-state="selected"][data-interaction="hover"]:not(
   [data-disabled]
 ) {