feat: add gemini-cli to x1 system and overlays

- Introduced `gemini-cli` as a CLI tool in the x1 configuration.
- Added a new overlay for `gemini-cli` package with npm dependencies.
- Removed `goose-cli` and `aider-chat` from the existing application list.

overlays/unstable/gemini-cli/package.nix

@@ -0,0 +1,50 @@
+{ lib
+, buildNpmPackage
+, fetchFromGitHub
+, nix-update-script
+,
+}:
+
+let
+  pname = "gemini-cli";
+  version = "0.1.4";
+in
+buildNpmPackage {
+  inherit pname version;
+
+  src = fetchFromGitHub {
+    owner = "google-gemini";
+    repo = "gemini-cli";
+    # Currently there's no release tag, use the `package-lock.json` to see
+    # what's the latest version
+    rev = "a8763abfb7eeb91bc48445a5e0a24ab0532a714d";
+    hash = "sha256-yRzTYr4LHmT9t93I0P4Ewx5kO1E7aeIPVxXvB3A1Ofc=";
+  };
+
+  npmDepsHash = "sha256-RwEQtlwNPSu6WiWPW5N1s7tUNuVjZogN5RTAmNXqjLU=";
+
+  fixupPhase = ''
+    runHook preFixup
+
+    # Remove broken symlinks
+    find $out -type l -exec test ! -e {} \; -delete 2>/dev/null || true
+
+    mkdir -p "$out/bin"
+    ln -sf "$out/lib/node_modules/@google/gemini-cli/bundle/gemini.js" "$out/bin/gemini"
+
+    patchShebangs "$out/bin" "$out/lib/node_modules/@google/gemini-cli/bundle/"
+
+    runHook postFixup
+  '';
+
+  passthru.updateScript = ./update.sh;
+
+  meta = {
+    description = "AI agent that brings the power of Gemini directly into your terminal";
+    homepage = "https://github.com/google-gemini/gemini-cli";
+    license = lib.licenses.asl20;
+    maintainers = with lib.maintainers; [ donteatoreo ];
+    platforms = lib.platforms.all;
+    mainProgram = "gemini";
+  };
+}