Adds nix/desktop.nix building the Electron renderer with buildNpmPackage
and wrapping nixpkgs' electron binary. Reuses .#default by setting
HERMES_DESKTOP_HERMES to its hermes binary, so the desktop's resolver
picks up the fully-wired nix hermes (venv, bundled skills/plugins,
runtime PATH) without reimplementing agent resolution.
- nix/desktop.nix: renderer + electron wrapper
- nix/hermes-agent.nix: finalAttrs form, exposes hermesDesktop in passthru
- nix/packages.nix: exposes .#desktop + adds to fix-lockfiles
- apps/desktop/package-lock.json: standalone hermetic lockfile
nix build .#desktop && nix run .#desktop both clean.