feat: restore legacy modal and drag behavior

src/MBN_STOCK_WEBVIEW.LegacyParityApp/Web/playout-ui.js

@@ -116,7 +116,10 @@
     takeOut.disabled = busy || !commandAvailable;
     backgroundNone.disabled = busy || playout.canChangeBackground !== true;
     backgroundFile.disabled = busy || playout.canChangeBackground !== true;
-    fadeDuration.disabled = busy || playout.canChangeBackground !== true;
+    // MainForm.Designer keeps panel3 (which owns ComboDi) invisible. Preserve
+    // the native fade value as read-only state, but never expose an operator
+    // interaction path from the WebView shell.
+    fadeDuration.disabled = true;
     backgroundNone.checked = playout.backgroundEnabled !== true;
     backgroundName.value = playout.backgroundEnabled === true
       ? (playout.backgroundFileName || "선택한 배경") : "배경없음";
@@ -149,12 +152,17 @@
   backgroundNone.addEventListener("change", function () {
     post("toggle-background", {});
   });
-  fadeDuration.addEventListener("change", function () {
-    post("set-fade-duration", { duration: Number(fadeDuration.value) });
-  });
-
   document.addEventListener("keydown", function (event) {
-    if (event.defaultPrevented || event.repeat || hasOpenDialog()) return;
+    if (event.defaultPrevented) return;
+    const legacyShortcut = event.key === "F2" || event.key === "F3" ||
+      event.key === "F8" || event.key === "Escape";
+    if (hasOpenDialog()) {
+      // ShowDialog/MessageBox own these keys. Consume browser defaults (notably
+      // Chromium's F3 Find Next) without invoking a MainForm playout shortcut.
+      if (legacyShortcut) event.preventDefault();
+      return;
+    }
+    if (event.repeat) return;
     if (event.key === "F2") {
       event.preventDefault();
       if (!backgroundFile.disabled) backgroundFile.click();