fix: reject missing local mindspace cover files

scripts/check-mindspace-cover.mjs

@@ -54,6 +54,17 @@ function hasCoverImageHint(html) {
   return true;
 }
 
+function missingLocalCoverPath(htmlPath, coverMeta) {
+  const cover = String(coverMeta?.cover ?? coverMeta?.image ?? '').trim();
+  if (!cover || /^https?:\/\//i.test(cover) || cover.startsWith('data:')) return null;
+  const clean = cover.split('?')[0].split('#')[0].replace(/^\.\//, '');
+  if (!clean || clean.startsWith('/') || clean.includes('\\')) return null;
+  const base = path.dirname(htmlPath);
+  const target = path.resolve(base, clean);
+  if (target !== base && !target.startsWith(`${base}${path.sep}`)) return clean;
+  return fs.existsSync(target) && fs.statSync(target).isFile() ? null : clean;
+}
+
 function auditCoverHtml(htmlPath, html) {
   const issues = [];
   if (!hasMindspaceCoverMeta(html)) {
@@ -76,6 +87,14 @@ function auditCoverHtml(htmlPath, html) {
     if (!String(coverMeta.accent ?? '').trim()) {
       issues.push({ level: 'warn', code: 'missing_accent', message: 'mindspace-cover 缺少 accent' });
     }
+    const missingCover = missingLocalCoverPath(htmlPath, coverMeta);
+    if (missingCover) {
+      issues.push({
+        level: 'error',
+        code: 'missing_cover_file',
+        message: `mindspace-cover 引用的本地文件不存在：${missingCover}`,
+      });
+    }
   }
   if (!hasCoverImageHint(html)) {
     issues.push({