- Remove dead overlays/default.nix (flake defines overlays inline)
- Remove orphaned overlays/mods/{beads,n8n}.nix (never imported)
- Remove docs/packages/notesmd-cli.md (package doesn't exist)
- Extract externalSkills submodule to shared-options.nix (eliminates
~100 lines of duplication across opencode/claude-code/pi modules)
- Fix lib output: use nixpkgs.lib directly instead of instantiating
a full nixpkgs just to get lib
- Add lib unit tests to flake checks
- Update stale comment in coding-rules.nix
Skills from flake inputs (e.g. Basecamp) were not being passed to
mkOpencodeSkills for the pi agent, so they never appeared in
~/.pi/agent/skills/. This adds the same externalSkills option that
the opencode agent module already has.
