The ports package was fully implemented but detect_openbsd.go still
returned nil candidates with a stale TODO. Wire up ports.New() so
OpenBSD systems can auto-detect their package manager.
Also adds:
- Unit tests for GetCapabilities with mock managers (base + full)
- Unit tests for Locker mutual exclusion
- Edge case tests for ports parser (empty input, whitespace, fallback)
- Minor dep updates (charmbracelet/ultraviolet, charmbracelet/x)
