refactor: simplify copyDirectoryContents implementation

Replaced manual glob and loop with a single fsCopy call from fs-extra. This improves performance, robustness against EMFILE errors, and significantly simplifies the code while maintaining the same behavior. Added a learning entry to .jules/refactor.md.

Co-authored-by: gonzaloriestra <14979109+gonzaloriestra@users.noreply.github.com>

Author: google-labs-jules[bot]

.jules/refactor.md

@@ -0,0 +1,4 @@
+## 2025-05-15 - Prefer native library utility for directory copy
+**Smell:** Manual loop and `glob` to copy a directory's contents when a standard utility already exists in the codebase.
+**Learning:** The previous manual implementation of `copyDirectoryContents` used `glob` + `Promise.all` with individual `copyFile` calls. This is not only more complex but could lead to EMFILE errors on large directories. Using `fsCopy` (which wraps `fs-extra.copy`) is simpler and more robust as it handles concurrency and path normalization natively.
+**Prevention:** Always check if a higher-level utility exists in the local `fs.ts` or the underlying `fs-extra` library before implementing manual directory traversal.

packages/cli-kit/src/public/node/fs.ts

@@ -717,21 +717,5 @@ export async function copyDirectoryContents(srcDir: string, destDir: string): Pr
     throw new Error(`Source directory ${srcDir} does not exist`)
   }
 
-  if (!(await fileExists(destDir))) {
-    await mkdir(destDir)
-  }
-
-  // Get all files and directories in the source directory
-  const items = await glob(joinPath(srcDir, '**/*'))
-
-  const filesToCopy = []
-
-  for (const item of items) {
-    const relativePath = item.replace(srcDir, '').replace(/^[/\\]/, '')
-    const destPath = joinPath(destDir, relativePath)
-
-    filesToCopy.push(copyFile(item, destPath))
-  }
-
-  await Promise.all(filesToCopy)
+  await fsCopy(srcDir, destDir)
 }