chore(node): update getUserPkgManager

see:
- https://stackoverflow.com/a/69301988
- pnpm/pnpm#3985
- pnpm/pnpm#4317

cli/src/utils/getUserPkgManager.ts

@@ -1,11 +1,35 @@
 export type PackageManager = "npm" | "pnpm" | "yarn";
 
+/**
+ * @link https://stackoverflow.com/a/69301988
+ * 
+ * @returns best guess at user's package manager
+ */
 export const getUserPkgManager: () => PackageManager = () => {
-  // This environment variable is set by npm and yarn but pnpm seems less consistent
-  const userAgent = process.env.npm_config_user_agent;
+    // This environment variable is set by npm and yarn but pnpm seems less consistent
+    const agent = process.env.npm_config_user_agent;
 
-  if (userAgent?.startsWith("yarn")) return "yarn";
-  if (userAgent?.startsWith("pnpm")) return "pnpm";
+    if (!agent) {
+        // This environment variable is set on Linux but I'm not sure about other OSes.
+        const parent = process.env._;
 
-  return "npm";
+        if (!parent) {
+            // No luck, assume npm
+            return "npm";
+        }
+
+        if (parent.endsWith("pnpx") || parent.endsWith("pnpm")) return "pnpm";
+        if (parent.endsWith("yarn")) return "yarn";
+
+        // Assume npm for anything else
+        return "npm";
+    }
+
+    const [program] = agent.split("/");
+
+    if (program === "yarn") return "yarn";
+    if (program === "pnpm") return "pnpm";
+
+    // Assume npm
+    return "npm";
 };