fix: remove broken eigent reference

The eigent package directory was deleted in 96f5d7f (which was titled
"chore: update n8n, openwork, vibetyper") but the callPackage reference
in pkgs/default.nix and the row in docs/packages/README.md were left
behind. As a result `nix build .#eigent` and `nix flake check` failed
with "undefined variable" errors when the eigent attribute was forced.

Drop both references so the package set evaluates cleanly.

pkgs/default.nix

@@ -18,7 +18,6 @@ in {
 
   sidecar = pkgs.callPackage ./sidecar {};
   td = pkgs.callPackage ./td {};
-  eigent = pkgs.callPackage ./eigent {};
   hyprpaper-random = pkgs.callPackage ./hyprpaper-random {};
   launch-webapp = pkgs.callPackage ./launch-webapp {};
   mem0 = pkgs.callPackage ./mem0 {};