fix(plugin-typedoc): link error and empty dir labels in sidebar

[SoonIter]

Summary

1. fix the link jump error (only exist in mdxRs: true)
2. fix the dir empty labels (caused by index convention refactor)

        function getDirLabelName(): string {
          let dirName;

          if (
            typeof label === 'string' &&
            label.startsWith(DEFAULT_DIRNAME_PREFIX)
          ) {
            dirName = label.replace(DEFAULT_DIRNAME_PREFIX, '');
          }

          // 1. { "label": "DIR", type: "dir" } in _meta.json
          if (!dirName && label) {
            return label;
          }
          // 2. H1 or frontmatter title in md
          if (title) {
            return title;
          }
          // 3. fallback to fs dirname
          return dirName ?? '';
        }

3. refactor plugin-typedoc, generate sidebar with _meta.json

Related Issue

closes #1603
closes #1629

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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