fix(package-manager): ignore managed npm folders in cloud sync

closes #4763

packages/coding-agent/src/utils/paths.ts

@@ -1,5 +1,6 @@
 import { realpathSync } from "node:fs";
 import { isAbsolute, relative, resolve as resolvePath, sep } from "node:path";
+import { spawnProcessSync } from "./child-process.ts";
 
 /**
  * Resolve a path to its canonical (real) form, following symlinks.
@@ -55,3 +56,20 @@ export function formatPathRelativeToCwdOrAbsolute(filePath: string, cwd: string)
 	const absolutePath = resolveAgainstCwd(filePath, cwd);
 	return (getCwdRelativePath(absolutePath, cwd) ?? absolutePath).split(sep).join("/");
 }
+
+export function markPathIgnoredByCloudSync(path: string): void {
+	const attrs =
+		process.platform === "darwin"
+			? ["com.dropbox.ignored", "com.apple.fileprovider.ignore#P"]
+			: process.platform === "linux"
+				? ["user.com.dropbox.ignored"]
+				: [];
+
+	for (const attr of attrs) {
+		if (process.platform === "darwin") {
+			spawnProcessSync("xattr", ["-w", attr, "1", path], { encoding: "utf-8", stdio: "ignore" });
+		} else {
+			spawnProcessSync("setfattr", ["-n", attr, "-v", "1", path], { encoding: "utf-8", stdio: "ignore" });
+		}
+	}
+}