🧪 [testing improvement] Improve test coverage for purchase-order-cart-actions.js

[cmuench]

🎯 What: Improved test coverage for lib/commands/purchase-order-cart-actions.js.
📊 Coverage: Mocked handleError and formatOutput via jest.unstable_mockModule('../lib/utils.js') to add tests verifying the error handling paths and the early return formatting branches for the totals, shipping-methods, and payment-info commands. Also removed the unused cli-table3 mock and updated existing tests to assert against printTable.
✨ Result: Reached 100% statement, branch, and line coverage for purchase-order-cart-actions.js.

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PR created automatically by Jules for task 17970344490660117259 started by @cmuench

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