When set to true, the skill is hidden from the system prompt, preventing
agentic invocation. Users can still invoke explicitly via /skill:name.
Also fixes pre-existing test bug where source expectation was wrong.
Fixes#927
- Add progress callbacks to PackageManager for TUI status during install/remove/update
- Add extension conflict detection (tools, commands, flags with same names)
- Accept raw GitHub/GitLab URLs without git: prefix
- Add tests for package-manager.ts and resource-loader.ts
- Add empty fixture directories for skills tests
