Add llm-wiki plugin under Documentation

[praneybehl]

Adds llm-wiki under the Documentation section as an external-link entry (the plugin lives in its own repo, installable via /plugin marketplace add praneybehl/llm-wiki-plugin).

What it does

Implementation of Andrej Karpathy's LLM Wiki pattern as a Claude Code plugin. Ingested sources (papers, articles, transcripts, PDFs, notes) get compiled once into persistent, structured markdown pages; subsequent queries read the pre-synthesized wiki rather than re-chunking raw sources, so knowledge compounds over time.

Surface area

• llm-wiki skill (progressive-disclosure references)
• 5 slash commands: /wiki:init, /wiki:ingest, /wiki:query, /wiki:lint, /wiki:stats
• 4 bundled stdlib-only Python scripts: init, BM25 search with frontmatter filters, structural lint, size/shape stats
• Marketplace manifest — also installable via npx skills add praneybehl/llm-wiki-plugin

Happy to vendor a subtree copy under ./plugins/llm-wiki instead if the project prefers that over external links — let me know.