⚡ Bolt: Optimize SwiftUI property evaluation in CacheoutViewModel

[acebytes]

💡 What: Replaced eager array allocations and full collection reductions in selectedSize and hasSelection with .lazy.filter and .contains(where:).
🎯 Why: SwiftUI evaluates ObservableObject computed properties frequently during view updates. Eagerly filtering collections or summing sizes just to check if they are empty causes unnecessary intermediate array allocations and O(N) operations.
📊 Impact: Eliminates array allocations for selectedSize and converts hasSelection from two O(N) operations (with one allocation) to zero-allocation, short-circuiting O(N) evaluations, yielding a best-case O(1) performance.
🔬 Measurement: Profile the main thread with Instruments during rapid selection toggling; observe reduced memory churn and faster hasSelection property evaluation.

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PR created automatically by Jules for task 15231807748488771423 started by @acebytes

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