feat(11-02): skillGroupService() with CRUD, membership, inheritance, assignment, import/export
- Group CRUD: listGroups, getGroup, createGroup, updateGroup, deleteGroup (guards built-in)
- Member management: addMember, removeMember, listMembers
- Inheritance: addParent (with cycle detection BFS), removeParent, listParents
- resolveEffectiveSkills: BFS walk with visited-set guard for cycle safety
- assignGroup: installs all effective skills, tracks in agent_skills, returns installed/skipped/pendingPlugin
- removeGroup: set-difference uninstall with fs.rm() for file removal (not skillRegistryService.uninstall)
- listAgentGroups, listAgentSkills, getAgentEffectiveSkills
- exportGroup / importGroup: GroupExport v1 JSON with cycle check on import
Mikkel Georgsen
bebacf5406