- SkillCard: add isReadOnly and source props; hide update/rollback/install when isReadOnly
- SkillCard: show Native badge when isReadOnly or source=native
- SkillBrowser: remove agentSkillsDir state and text input from install dialog
- SkillBrowser: add selectedAgentId state for per-agent installed skills view
- SkillBrowser: add agentInstalledSkills query using skillGroupsApi.listAgentSkills
- SkillBrowser: split installed skills into managedSkills/nativeSkills sections
- SkillBrowser: render Managed/Native section headings when nativeSkills.length > 0
- SkillBrowser: uninstall dialog now carries agentId and calls skillRegistryApi.uninstall
- SkillBrowser: install dialog sends agentId directly (no agentSkillsDir text input)