iter(g102): 焦点陷阱下沉为共享助手

packages/skin/ui/src/modal.ts

@@ -1,6 +1,6 @@
 import { effect, h } from '@ui-arch/frame';
 import type { ModalProps } from './types.js';
-import { lockScroll, pushOverlay } from './overlay.js';
+import { lockScroll, pushOverlay, trapFocus } from './overlay.js';
 
 let seq = 0; // 实例序号：给标题生成唯一 id，供 aria-labelledby 关联
 
@@ -31,9 +31,6 @@ export function modal(props: ModalProps, ...children: unknown[]): HTMLElement {
   let lastFocus: HTMLElement | null = null; // 打开前焦点宿主，关闭时归还
   let release: (() => void) | null = null; // Esc 栈注销函数，关闭时释放
   let releaseLock: (() => void) | null = null; // 背景滚动锁解锁函数，全关才还原
-  const focusables = (): HTMLElement[] =>
-    Array.from(box.querySelectorAll<HTMLElement>('button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'))
-      .filter((el) => !el.hasAttribute('disabled')); // 弹窗内可聚焦元素（排除禁用）
   effect(() => {
     const open = props.open();
     overlay.classList.toggle('ua-open', open); // 显隐跟随信号
@@ -51,17 +48,6 @@ export function modal(props: ModalProps, ...children: unknown[]): HTMLElement {
       lastFocus = null;
     }
   });
-  overlay.addEventListener('keydown', (e: KeyboardEvent) => {
-    if (e.key !== 'Tab' || !props.open()) return; // 仅处理打开中的 Tab
-    const els = focusables();
-    if (els.length === 0) { e.preventDefault(); return; } // 无可聚焦元素：拦截 Tab 防焦点逃逸
-    const first = els[0];
-    const last = els[els.length - 1];
-    if (e.shiftKey && (document.activeElement === first || !box.contains(document.activeElement))) {
-      e.preventDefault(); last.focus(); // Shift+Tab 到首位时回绕到末尾
-    } else if (!e.shiftKey && (document.activeElement === last || !box.contains(document.activeElement))) {
-      e.preventDefault(); first.focus(); // Tab 到末位时回绕到开头
-    }
-  });
+  trapFocus(box, () => props.open()); // Tab 焦点陷阱：与 drawer 共用同一份实现
   return overlay;
 }