fix: prevent selecting disabled focused days (#2860)

Fixes a test-only regression from #2851: jsdom allows focusing a disabled day, which drops the `disabled` attribute (keeps `aria-disabled`), so `toBeDisabled` fails and `onSelect` fires in tests even though browsers don’t allow focusing disabled buttons.

Author: gpbl

src/DayPicker.test.tsx

@@ -9,7 +9,7 @@ import {
   nextButton,
   previousButton,
 } from "@/test/elements";
-import { fireEvent, render, screen } from "@/test/render";
+import { act, fireEvent, render, screen } from "@/test/render";
 import { setTestTime } from "@/test/setTestTime";
 import { user } from "@/test/user";
 import { defaultLocale } from "./classes/DateLib";
@@ -122,6 +122,31 @@ describe("when the grid is focused", () => {
   });
 });
 
+describe("when a disabled day is focused", () => {
+  test("keyboard and mouse interactions do not select it", async () => {
+    const disabledDay = new Date(2024, 8, 5);
+    const handleSelect = jest.fn();
+
+    render(
+      <DayPicker
+        defaultMonth={disabledDay}
+        disabled={[disabledDay]}
+        mode="single"
+        onSelect={handleSelect}
+      />,
+    );
+
+    const disabledElement = dateButton(disabledDay);
+    act(() => disabledElement.focus());
+
+    await user.keyboard("{Enter}");
+    await user.click(disabledElement);
+
+    expect(handleSelect).not.toHaveBeenCalled();
+    expect(disabledElement).toHaveAttribute("aria-disabled", "true");
+  });
+});
+
 describe("when navigation is disabled", () => {
   beforeEach(() => {
     jest.useFakeTimers();

src/DayPicker.tsx

@@ -242,6 +242,9 @@ export function DayPicker(initialProps: DayPickerProps) {
       e.preventDefault();
       e.stopPropagation();
       setFocused(day);
+      if (m.disabled) {
+        return;
+      }
       select?.(day.date, m, e);
       onDayClick?.(day.date, m, e);
     },