Accordion: allow validation messages to overflow in opened items (T1327641)

[pharret31]

No description provided.

[Copilot]

Pull request overview

This PR updates the DevExtreme Accordion’s runtime styling so validation messages (and other content) can visually overflow outside an opened item after the expand animation completes, and adds QUnit coverage to lock in the expected behavior.

Changes:

• Reset inline overflow on items (and their bodies) when a height update/animation starts, so closing/opening transitions don’t keep overflow: visible.
• Apply overflow: visible to opened items (and their bodies) once the open animation finishes.
• Add QUnit tests covering opened/closed behavior, multiple mode, close-start reset, post-animation application, and reopen restoration.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/devextreme/testing/tests/DevExpress.ui.widgets/accordion.tests.js	Adds a new test module validating overflow behavior across open/close scenarios and animation timing.
packages/devextreme/js/__internal/ui/accordion.ts	Resets overflow at animation start and sets overflow: visible for opened items after animation completion.