GitHub MCP plugin auth fails: 'does not support dynamic client registration'

Bug

The github@claude-plugins-official MCP plugin consistently fails to authenticate.

Steps to Reproduce

1. Enable the github@claude-plugins-official plugin
2. Run /mcp and select "Authenticate" for the GitHub MCP server
3. Authentication fails immediately

Error

Plugin:github:github MCP Server

Status: △ needs authentication
Auth: ✘ not authenticated
URL: https://api.githubcopilot.com/mcp/
Config location: Dynamically configured

Error: SDK auth failed: Incompatible auth server: does not support dynamic client registration

Expected Behavior

The GitHub MCP plugin should authenticate successfully and expose GitHub tools.

Environment

• Claude Code CLI (macOS, Darwin 23.5.0)
• Plugin: github@claude-plugins-official
• Multiple attempts, consistently reproducible