Generate comprehensive statistics about your knowledge graph.

By default, returns aggregate stats across the whole graph. Use -k/--key to
restrict output to a single document's record; all -f formats apply.

Provides analytics including:
- Overview: document count, node count, path count
- Document stats: sections, paragraphs, top documents
- Reference stats: block/inline refs, orphans, leaves, most referenced
- Size stats: lines, words, largest documents
- Structure stats: lists, code blocks, tables, quotes
- Network analysis: connectivity, most connected documents
