feedback6: Esc in the 自选 picker closes only the picker, like its 取消 (GitHub #284 by @Xinglan233, idea from PR #286)

- The 干员调配 overlay's capture-phase Esc closed the whole overlay while a 自选 picker was open (it only gave way to a
  .modal; the picker is a .diy-pick section without its own key handling), so one Esc went back to the lobby.
- DiyPicker registers its own capture-phase Escape handler (calls onClose, as 取消 and the × do; skipped while a .modal
  — the 导入 dialog — is open, which handles Esc first); loadout.js returns early on Escape while a .diy-pick is open.
  The second Esc closes the overlay as before. Saved picks are untouched (the draft is dropped, as with 取消).
- test/ui/diy.e2e.test.js: a real-server browser test that needs no art (5阶 slot, then a 6阶 slot with Esc pressed in
  the search field): the picker closes, the overlay and its four slots stay, sp.pref.diy is unchanged, the next Esc
  closes the overlay. Fails on the parent (「Esc keeps the 干员调配 overlay」), passes here.
- Tests: SP_E2E=1 diy.e2e (the new test) 1 / 1; client-static, i18n, ui/diy*, ui/loadout* 369 / 369; eslint clean.

public/js/screens/loadout.js

@@ -550,6 +550,7 @@ function LoadoutScreen({ st }) {
     const onKey = (e) => {
       if (e.ctrlKey || e.metaKey || e.altKey) return;
       if (document.querySelector('.modal')) return; // a confirm dialog handles its own keys
+      if (e.key === 'Escape' && document.querySelector('.diy-pick')) return; // the 自选 picker's Esc closes only the picker (diy.js)
       const typing = e.target && /^(INPUT|SELECT|TEXTAREA)$/.test(e.target.tagName);
       if (e.key === 'Escape') { e.preventDefault(); e.stopImmediatePropagation(); closeLoadout(); return; }
       if (typing) return;