chore: shorten server.json description for MCP registry (100 char limit)

Author: Bortlesboat

server.json

@@ -2,7 +2,7 @@
   "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
   "name": "io.github.Bortlesboat/bitcoin-mcp",
   "title": "Bitcoin MCP",
-  "description": "Bitcoin MCP server — 49 tools for fees, mempool, blocks, mining, price, address history. Zero config.",
+  "description": "49 Bitcoin tools for AI agents: fees, mempool, blocks, mining, price. Zero config.",
   "repository": {
     "url": "https://github.com/Bortlesboat/bitcoin-mcp",
     "source": "github"