Add a skills.sh-backed source adapter for the Hermes Skills Hub.
The new adapter uses skills.sh search results for discovery, falls back to
featured homepage links for browse-style queries, and resolves installs /
inspects through the underlying GitHub repo using common Agent Skills
layout conventions. Also expose skills-sh in CLI source filters and add
regression coverage for search, alias resolution, and source routing.
- unified_search and GitHubSource.search dedup: replace naive
`trust_level == "trusted"` check with ranked comparison so
"builtin" results are never overwritten by "trusted" or "community"
- Add 43 unit tests covering _parse_frontmatter_quick, trust_level_for,
HubLockFile CRUD, TapsManager ops, LobeHub _convert_to_skill_md,
unified_search dedup (with regression test), and append_audit_log
