⚡ Bolt: Optimize LINQ Sum on hot paths

[google-labs-jules]

💡 What:
Replaced LINQ .Sum() calls calculating unusedSupply, unmetDemand, and totalBidCost in NetworkSimulationEngine.cs with standard foreach loops.

🎯 Why:
The LINQ .Sum() extension method creates an implicit lambda delegate and typically allocates an enumerator each time it is called. Since these are evaluated iteratively within the primary AnalyzeContextResults loop of the simulation engine, they cause measurable garbage collection pressure and CPU overhead on a hot path.

📊 Impact:
Eliminates $O(N)$ delegate allocations per analysis loop, directly reducing GC pauses and slightly improving overall simulation throughput for large networks.

🔬 Measurement:
Run dotnet test tests/MedWNetworkSim.Tests/MedWNetworkSim.Tests.csproj to confirm functional determinism is preserved identically.

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PR created automatically by Jules for task 7901382992333654466 started by @wnj00524

[google-labs-jules]

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