name: lookup description: Look up one Zotero item by citekey.
Use the Zotero MCP server to look up an item by its exact citekey.
If the user did not provide a citekey, ask for one.
Use the Zotero lookup tool with the citekey.
Rules:
- Treat this as exact citekey lookup, not broad search.
- Do not invent metadata.
- If Zotero has no entry for the citekey, say so clearly.
- When an item is found, return a short metadata summary and include whether fulltext is available.