[fix] resolve empty overview links at build time

- onEmptyLinkMatch resolved the target from the page directory instead
  of the docs root, so [](api/...) links stayed empty and unresolved
- now resolves from the docs root and emits a root-absolute href
  without the .md/.mdx extension, matching normalizeMarkdownMdLinks
- guard against a missing file or absent sidebar_label to avoid build crash

Author: serhiipylypchuk1991

docusaurus.config.js

@@ -91,8 +91,16 @@ const readFile = (workingDir, filePath) => {
 const onEmptyLinkMatch = (data, { key, fullMatch, dir }) => {
 	const filePath = fullMatch.substring(fullMatch.indexOf('(') + 1, fullMatch.length - 1);
 	if (filePath.indexOf('.md') !== -1 || filePath.indexOf('.mdx') !== -1 || filePath.indexOf('.') === -1) {
-		const data = readFile(dir, filePath);
-		return data ? `[${/.*sidebar_label: (.+)/g.exec(data)[1]}]${fullMatch.match(/\(\D+\)/g)[0]}` : fullMatch;
+		// Links are written root-relative (e.g. api/events/add-field-event.md), so resolve
+		// the target from the docs root rather than the page's own directory.
+		const fileContent = readFile(path.join(__dirname, 'docs'), filePath);
+		if (!fileContent) return fullMatch;
+		const labelMatch = /sidebar_label: (.+)/.exec(fileContent);
+		if (!labelMatch) return fullMatch;
+		// Emit a root-absolute href without the .md/.mdx extension, matching how
+		// normalizeMarkdownMdLinks rewrites ordinary links.
+		const href = '/' + filePath.replace(/^\.?\/+/, '').replace(/\.(md|mdx)(?=$|#)/, '');
+		return `[${labelMatch[1].trim()}](${href})`;
 	}
 	return fullMatch;
 };