fix: use bun to run mcp-server.cjs instead of node shebang (fixes #1648)

The mcp-server.cjs script requires bun:sqlite, a Bun-specific built-in
that is unavailable in Node.js. When Claude Code spawns the script using
the shebang (#!/usr/bin/env node), the import fails with:
  Error: Cannot find module 'bun:sqlite'

Fix: explicitly invoke bun as the command and pass the script as an arg,
so the correct runtime is used regardless of the shebang line.

plugin/.mcp.json

@@ -2,7 +2,8 @@
   "mcpServers": {
     "mcp-search": {
       "type": "stdio",
-      "command": "${CLAUDE_PLUGIN_ROOT}/scripts/mcp-server.cjs"
+      "command": "bun",
+      "args": ["${CLAUDE_PLUGIN_ROOT}/scripts/mcp-server.cjs"]
     }
   }
 }