[Tests] Add coverage for vscode recommendation utility

[gonzaloriestra]

WHY are these changes introduced?

This PR introduces unit tests for the vscode recommended extensions utility addRecommendedExtensions to improve test coverage and ensure its correct behavior across potential future refactors.

WHAT is this pull request doing?

We added three targeted unit test cases in packages/cli-kit/src/public/node/vscode.test.ts to fully cover:

1. When the .vscode directory does not exist, verifying that no action is taken.
2. When the .vscode directory exists but extensions.json is missing, verifying it gets created with the expected recommendations.
3. When both exist, verifying that new recommendations are correctly appended without erasing existing ones or other keys in the file.

All tests utilize a real isolated temporary directory and no mocked file system.

How to test your changes?

CI

Post-release steps

None.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

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PR created automatically by Jules for task 14603922283518488159 started by @gonzaloriestra

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