feat(md-deck): Add fallback copy dialog for clipboard failure

src/components/md-deck/DeckHeader.tsx

@@ -1,3 +1,5 @@
+import { Show, createSignal, onMount } from "solid-js";
+import { Portal } from "solid-js/web";
 import type { DeckStore } from "./hooks/deckStore";
 
 export interface DeckHeaderProps {
@@ -9,8 +11,28 @@ export interface DeckHeaderProps {
  */
 export function DeckHeader(props: DeckHeaderProps) {
   const { store } = props;
+  const [showCopyFallback, setShowCopyFallback] = createSignal(false);
+  const [fallbackCode, setFallbackCode] = createSignal("");
+  let textareaRef: HTMLTextAreaElement | undefined;
+
+  onMount(() => {
+    if (showCopyFallback() && textareaRef) {
+      textareaRef.focus();
+      textareaRef.select();
+    }
+  });
+
+  const handleCopy = () => {
+    store.actions.copyCode((code) => {
+      setFallbackCode(code);
+      setShowCopyFallback(true);
+    });
+  };
+
+  const closeFallback = () => setShowCopyFallback(false);
 
   return (
+    <>
       <div class="flex items-center gap-2 border-b border-gray-200 pb-2 mb-4">
         {/* 编辑按钮 */}
         <button
@@ -34,11 +56,48 @@ export function DeckHeader(props: DeckHeaderProps) {
 
         {/* 复制代码按钮 */}
         <button
-        onClick={() => store.actions.copyCode()}
+          onClick={handleCopy}
           class="px-2 py-1 rounded text-xs font-medium transition-colors cursor-pointer bg-purple-100 text-purple-600 hover:bg-purple-200"
         >
           📋 复制代码
         </button>
       </div>
+
+      {/* 剪贴板不可用时的手动复制弹窗 */}
+      <Show when={showCopyFallback()}>
+        <Portal>
+          <div
+            class="fixed inset-0 bg-black/50 z-60 flex items-center justify-center p-4"
+            onClick={closeFallback}
+          >
+            <div
+              class="bg-white rounded-lg shadow-xl w-full max-w-lg p-4"
+              onClick={(e) => e.stopPropagation()}
+            >
+              <h3 class="font-bold mb-2">复制代码</h3>
+              <p class="text-sm text-gray-600 mb-3">
+                自动复制失败（当前站点可能不是 HTTPS），请手动复制下面的代码：
+              </p>
+              <textarea
+                ref={textareaRef}
+                readonly
+                value={fallbackCode()}
+                class="w-full h-40 border border-gray-300 rounded px-3 py-2 text-xs font-mono bg-gray-50 resize-none"
+                onFocus={(e) => e.currentTarget.select()}
+                onClick={(e) => e.currentTarget.select()}
+              />
+              <div class="flex justify-end gap-2 mt-3">
+                <button
+                  onClick={closeFallback}
+                  class="px-3 py-1.5 rounded text-sm font-medium cursor-pointer bg-gray-100 text-gray-700 hover:bg-gray-200"
+                >
+                  关闭
+                </button>
+              </div>
+            </div>
+          </div>
+        </Portal>
+      </Show>
+    </>
   );
 }

src/components/md-deck/hooks/deckStore.ts

@@ -145,7 +145,7 @@ export interface DeckActions {
   clearError: () => void;
 
   generateCode: (backLayersStr?: string) => string;
-  copyCode: (backLayersStr?: string) => Promise<void>;
+  copyCode: (fallback?: (code: string) => void) => Promise<void>;
 
   setExporting: (exporting: boolean) => void;
   exportDeck: () => void;
@@ -514,15 +514,19 @@ export function createDeckStore(initialSrc: string = ""): DeckStore {
     return parts.join("");
   };
 
-  const copyCode = async (backLayersStr?: string) => {
+  const copyCode = async (fallback?: (code: string) => void) => {
-    const code = generateCode(backLayersStr);
+    const code = generateCode();
     try {
       await navigator.clipboard.writeText(code);
       alert("已复制到剪贴板！");
     } catch (err) {
       console.error("复制失败:", err);
+      if (fallback) {
+        fallback(code);
+      } else {
         alert("复制失败，请手动复制");
       }
+    }
   };
 
   const setExporting = (exporting: boolean) =>