Claude subscription / Claude Code keys are OAuth tokens and authenticate with
Authorization: Bearer, not x-api-key. mcpd's server adapter only sent x-api-key,
so registering an OAuth key as a fallback Llm 401'd ("invalid x-api-key").
Mirror the mcplocal client adapter's isOAuth switch so an OAuth key works as a
server-side anthropic fallback.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>