Reproduction:
- Enable `frontend-design@claude-code-plugins`
- Enable `frontend-design@claude-plugins-official`
- Start OpenClaude with both marketplace plugins active
- Both plugins load, but downstream command and skill scopes key off the short plugin name, so both collapse to `frontend-design` and can interfere with interactive startup
Fix:
- Collapse duplicate marketplace plugins by short name during merge
- Keep the enabled copy when enabled state differs; otherwise keep the later config entry
- Add regression coverage for both cases
