Modal default focus prioritizes close button over content elements

When a Modal opens, focus currently defaults to the close (X) button in the header, regardless of what interactive elements exist within the modal content. This behavior is a bit counterintuitive. The default focus should prioritize the first meaningful, focusable element within the modal body (e.g., a primary action button) rather than header controls.

This request originates from a Red Hat product team. There is no hard deadline.

Jira Issue: PF-2526

首先定位 Modal 的实现及其现有的 focus-management 测试，然后复现 modal body 中包含交互内容时的默认焦点行为。完成的标准是：焦点优先定位到 body 中第一个有意义的可聚焦元素，而不是 header close button，同时保留预期的 modal 焦点行为。