bug: installation fails, checks public npm registry instead of github npm registry

[fcakyon]

@syucream I correctly set my user token, bot token, and GitHub PAM with read registry permission, but the installation fails. Here is the complete log on Claude Desktop:

2025-07-04T08:45:27.716Z [slack] [info] Initializing server... { metadata: undefined }
2025-07-04T08:45:27.733Z [slack] [info] Using MCP server command: /Users/fca/.nvm/versions/node/v22.15.0/bin/npx with args and path: {
  metadata: {
    args: [ '-y', '@ubie-oss/slack-mcp-server@0.1.1', [length]: 2 ],
    paths: [
      '/Users/fca/.nvm/versions/node/v22.15.0/bin',
      '/usr/local/bin',
      '/opt/homebrew/bin',
      '/usr/bin',
      '/usr/bin',
      '/bin',
      '/usr/sbin',
      '/sbin',
      [length]: 8
    ]
  }
} %o
2025-07-04T08:45:27.733Z [slack] [info] Server started and connected successfully { metadata: undefined }
2025-07-04T08:45:27.736Z [slack] [info] Message from client: {"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"claude-ai","version":"0.1.0"}},"jsonrpc":"2.0","id":0} { metadata: undefined }
npm error code E404
npm error 404 Not Found - GET https://registry.npmjs.org/@ubie-oss%2fslack-mcp-server - Not found
npm error 404
npm error 404  '@ubie-oss/slack-mcp-server@0.1.1' is not in this registry.
npm error 404
npm error 404 Note that you can also install from a
npm error 404 tarball, folder, http url, or git url.
npm error A complete log of this run can be found in: /Users/fca/.npm/_logs/2025-07-04T08_45_27_927Z-debug-0.log
2025-07-04T08:45:28.536Z [slack] [info] Server transport closed { metadata: undefined }
2025-07-04T08:45:28.536Z [slack] [info] Client transport closed { metadata: undefined }
2025-07-04T08:45:28.536Z [slack] [info] Server transport closed unexpectedly, this is likely due to the process exiting early. If you are developing this MCP server you can add output to stderr (i.e. `console.error('...')` in JavaScript, `print('...', file=sys.stderr)` in python) and it will appear in this log. { metadata: undefined }
2025-07-04T08:45:28.536Z [slack] [error] Server disconnected. For troubleshooting guidance, please visit our [debugging documentation](https://modelcontextprotocol.io/docs/tools/debugging) { metadata: { context: 'connection', stack: undefined } }
2025-07-04T08:45:28.536Z [slack] [info] Client transport closed { metadata: undefined }