feat(home): add zed, cursor, and vscodium (#1)

home/common/programs/default.nix

@@ -11,6 +11,7 @@
     ./zsh.nix
     ./nix.nix
     ./neovim
+    ./editors.nix
     ./rust.nix
     ./elixir.nix
     ./nodejs.nix

home/common/programs/editors.nix

@@ -0,0 +1,12 @@
+{ pkgs, ... }:
+{
+  # Trialling GUI editors alongside neovim, for reviewing agent-generated
+  # diffs. Drop the ones that don't stick.
+  home.packages = with pkgs; [
+    zed-editor
+    code-cursor
+    # VSCodium and Cursor both default to Open VSX, which carries
+    # GitHub.vscode-pull-request-github. Zed has no PR review at all.
+    vscodium
+  ];
+}