test(server): isolate the unset Claude home case from CLAUDE_CONFIG_DIR

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CeWArRh6FDJGzjGYecyi7A
9b8a6af3c1Claude committed on 9/26/2026, 12:15:05 AMparent650b06c
1 file changedLine totals unavailable